r r r r r r r r r REPORT ON THE EDWARDS AQUIFER SAN ANTONIO REGION, TEXAS DONALD G. RAUSCHUBER & ASSOCIATES, INC. AUSTIN, TEXAS MAY 18, 1995

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1 L REPORT ON THE EDWARDS AQUFER SAN ANTONO REGON, TEXAS PREPARED BY DONALD G. RAUSCHUBER & ASSOCATES, NC. AUSTN, TEXAS MAY 18, 1995

2 TABLE OF CONTENTS LST OF TABLES LST OF FGURES TABLE OF CONTENTS PAGE SECTON EXPLANATON OF THE EDWARDS AQUFER Geneal Desciption of the Edwads Aquife Fomation of the San Antonio Region of the Edwads Aquife Rechage Zone: San Antonio Region of the Edwads Aquife Atesian Zone: San Antonio Region of the Edwads Aquife Goundwate Stoage Goundwate Movement Histoical Rechage Histoical Pumpage Sping Flows -33 SECTON EDWARDS AQUFER -- AN UNDERGROUND RVER? -1 SECTON EDWARDS AQUFER - WATER QUALTY SSUES i ii iii -1 SECTON V EFFECTS OF SELECTED PUMPAGE ON SPRNG FLOW V-1 SECTON V REVSED EMERGENCY WTHDRAWAL REDUCTON PLAN V-1 BBLOGRAPHY B-1 APPENDX A A-1 i

3 L TABLE 7.1 TABLE 7.2 TABLE 8.1 TABLE 8.2 LST OF TABLES TOTAL ANNUAL RECHARGE BY CONTRBUTNG WATERSHED TO THE EDWARDS AQUFER - SAN ANTONO REGON TOTAL ANNUAL RECHARGE BY CONTRBUTNG FLOW UNT TO THE EDWARDS AQUFER - SAN ANTONO REGON TOTAL ANNUAL PUMPAGE AND SPRNG FLOW DSCHARGE FROM THE EDWARDS AQUFER - SAN ANTONO REGON NUMBER OF WELLS N THE EDWARDS AQUFER, SAN ANTONO REGON, FOR WHCH RECORDS WERE OBTANED FROM THE TEXAS WATER COMMSSON CENTRAL RECORDS FLE (11/91) ii PAGE

4 L FGURE 2.1 FGURE 2.2A FGURE 2.2B FGURE 2.2C FGURE 2.3 FGURE 2.4 FGURE 2.5 FGURE 4.1 FGURE 5.1 FGURE 5.2 FGURE 7.1 FGURE 7.2 FGURE 8.1 LST OF FGURES PAGE DEPOSTONAL PROVNCES AND GEOLOGC STRUCTURE -3 HYDROGEOLOGC CROSS-SECTONS FOR SECTONS A-A' AND B-B' -5 HYDROGEOLOGC CROSS-SECTON FOR SECTON G-G' -7 HYDROGEOLOGC CROSS-SECTON FOR SECTON ZZ-ZZ' -8 GEOHYDROLOGC SECTON B-B' GEOHYDROLOGC SECTON D-D' LOCATON OF THE SAN ANTONO, EDWARDS AQUFER, PHYSOGRAPHC REGONS, AND DRANAGE BASNS THAT CONTRBUTE TO RECHARGE ll MAJOR FAULTS -15 LOCATONS OF SELECTED GEOLOGC STRUCTURES RESTRCTNG AND CONVEYNG GROUND WATER -19 STORAGE AND FLOW UNTS AND AREAS OF FLOW ACROSS EXTERNAL BOUNDARES -2 GRAPH OF ANNUAL RECHARGE TO THE EDWARDS AQUFER - SAN ANTONO REGON FOR 1934 THROUGH GRAPH OF ANNUAL RECHARGE BY STORAGE UNT TO THE EDWARDS AQUFER - SAN ANTONO REGON FOR 1934 THROUGH LOCATON OF MAJOR WELLS -37 iii

5 . ' REPORT ON THE EDWARDS AQUFER SAN ANTONO REGON, TEXAS MAY 18, 1995 SECTON. Explanation of the Edwads Aquife 1. Geneal Desciption of the Edwads Aquife (Balcones Fault Zone) The entie Edwads Aquife (Balcones Fault Zone) extends fom Salado, Texas, in Bell County, though Austin (Tavis County), San Macos (Hays County), New Baunfels (Comal County), San Antonio (Bexa County), Hondo (Medina County), and Uvalde (Uvalde County) to Backettville (Kinney County). The Edwads Aquife is appoximately 26 miles (mi.) long and vaies in width fom 5 to 4 mi. and cosses seveal steams in five majo ive basins, including the Nueces, San Antonio, Guadalupe, Coloado and Bazos Rive basins. The Aquife is segmented into thee pats. The Nothen segment of the Edwads Aquife extends fom Salado to the Coloado Rive in Austin. The Baton Spings segment of the Edwads Aquife extends fom the Coloado Rive to a gound wate "high" located between the cities of Buda (Hays County) and Kyle (Hays County) The San Antonio Region of the Edwads Aquife extends fom this gound wate high to nea Backettville. Each segment of the Aquife has majo echage souces and natual dischage points. Fo the most pat, each segment acts independently of the othe, although thee is technical evidence that limited quantities of wate may flow between adjacent segments unde cetain hydogeologic conditions. -1

6 . E 2. Fomation of the San Antonio Region of the Edwads Aquife The Edwads Limestone, fomed in the Ealy Cetaceous, is exposed thoughout the Edwads Plateau. This limestone fomation in the San Antonio Region consists of 4 to 6 ft of thin to massivebedded cabonate ocks and is compised of seveal statigaphic zones containing pemeable beds with well developed vugqy poosity 2 n some aeas, these zones ae vetically sepaated by beds of dense to chalky limestone having little to modeate pemeabilityl and poosity. At some locations, the pemeable 4 stata ae hydaulically inteconnected by open, inclined factues. While at othe locations, the lateal continuity of the pemeable stata is made discontinuous by vetical/high angle faults that displace the entie thickness of the Edwads Limestone. The Edwads Limestone was fomed on the shoes of ancient seas. Ealy Cetaceous baie eefs, such as stuat City Reef and Devils Rive Reef caused sediments compising the Edwads Limestone to deposit, foming seveal limestone platfoms (Figue 2.1). The Cental Texas Platfom and the San Macos Platfom developed to the noth and west of the Stuat City Reef and the Maveick Basin (platfom) developed due to the location of the Devils Rive Reef. These platfoms wee ceated by cyclic deposition of mateials Statigaphic - The aangement of ocks in layes o stata. Poosity - The atio of the aggegate volume of intestices (openings) in a ock o soil to its total volume, usually stated as a pecentage. Pemeability - The capacity of a ock, soil o sediment to tansmit a fluid. Pemeable - Rock, soil o sediment having a textue that pemits wate to move though it peceptibiy unde the head diffeences odinaily found in subsuface wate. A pemeable ock has communicating intestices (openings) of capillay o supe-capillay size. -2

7 DEPOSTON STRUCTURE. 1 2 MLES -,-L.- -- i 1 2 KLOMETERS Figue 2.1 Depositional Povinces and Geologic stuctue. (Souce: USGS Repot ) -3

8 behind (noth and west) the eefs. The sediments compising the cabonate Edwads Limestone wee fomed by the tansgessing and egessing seas. Afte the seas eceded, the platfoms wee ' popagated by tidal and subtidal sediments oiginating fom the noth and west. Evapoites wee deposited on these vast low lying platfoms, futhe contibuting to thei fomation. Duing the late Edwads time ea, eosion emoved moe than 1 ft of the deposits fom the San Macos platfom esulting in extensive kastification 5 of the limestones and dolomites. Poosity and kastification of the limestones was futhe developed by continual cycles of cabonate deposition and ainfall, which cemented and leached the sediments (USGS 1986). t Though the deposition and eosion pocess, the Cetaceous statigaphic units of the Edwads Limestone in the San Antonio Region wee fomed (Rose 1972). These units, shown in Fique 2.1, include the Maveick Basin, Devils Rive Tend, and San Macos Platfom. The geologic unit located below the Edwads Limestone (Aquife) is the Glen Rose Fomation. This fomation consists of mal, shale, and dolomite in its highe elevation pats and massive bedded limestone and dolomite in its lowe elevation sections. The uppe sections of Glen Rose Fomation, which has low to vey low pemeability, is the lowe confining unit of the Edwads Aquife. The top of the Edwads Aquife is confined by the Del Rio Clay. This clay stata is elatively impemeable and pevents the vetical movement of wate to and fom the Edwads Aquife within the atesian zone. The Edwads Limestone of the San Antonio Region is extensively faulted as shown in the coss-sections pesented in Fiques 2.2A 5 Kastification - Action by wate, mainly chemical but also mechanical, that poduces featues of a kast topogaphy including caves, sink holes, and solution channels. -4

9 FEET SEA LEVEL FEET A f 2 i' Ko J C1 UllES,, & KLOU( le"s SEA LEVEL 2 1 B.() EXPLANATON GEOLOGC UNTS Kt Kau Kobd Taylo Mal Austin Goup Kg Eagle Fod Goup, Buda Llmoslono, ond Dol Rio Clay o' ',.o!jf,,.# o'b :\-' Ko Edwado Goup ol Roso ( 1972), undllfoontlalod and ovelying Geogolown FomaUon Kp Poaon Fomation of Edwad:. Goup of Rose (1972), ncludes Geogetown Fomation Kk Kalno Fomation of Edwads Goup of Rooe (172) Ko Olen Roae Fomation (lncludeo olde fomallono n oome cuoao) D CONFNNG BEDS 1 2 :1 ULES f--, i S Cl CLOUElEA EDWARDS AQUFER YEilliCAL CALE ORCAtl.Y EXAOOERAtt:O FiguJe A' 8' a' a"::,,fj o"',o, <:>+ otf:i, tb <:>+ o 'b 'S :\-' () Wato lovol FAUL T-Aowo ohow dlecllon of movemenl 2.2A Hydogeologic Coss-sections fo Sections A-A' and B-Bf' (Souce: USGS 1985) -5

10 though 2.2c6 (USGS 1985). These faults, geneally downthown to the south and southeast, and tending east-notheast (USGS 1986), fom a complex system of fault blocks that ae diffeentially otated and ise towad the San Macos Platfom. Along the stike 7 of some majo faults, the displacement acoss the fault plane is sufficient to disupt the continuity of the Aquife. Maximum fault displacement is epoted to be 6 ft. at the comal Spings Fault, with fault displacement aveaging 2 ft. to the west in Medina and Uvalde Counties (Klemt et al 1979) Typical geologic cosssections of the Edwads Aquife illustating discontinuity of the Aquife ae shown in Figues 2.3 and 2.4 (TDWR 1979). Some coss faults intesect at acute angles. This complex system of faults include baie faults. These faults function as contols in the Aquife which locally divet the diection of gound wate flow in the block updip fom the baie fault to a diection paallel to the stike of the fault (Patteson 199). Whee faults faces ae contiguous, gound wate can flow nomal to the fault plane if pemeable conditions exist. The San Antonio Region of the Edwads Aquife is shown in Figue Within this Region (efeed to heein as the "Edwads Aquife" o the "San Antonio Region"), the lowe confining bed of the Edwads Aquife is the uppe membe of the Glen Rose fomation, and the uppe confining bed is the Del Rio Clay. As stated above, these confining units typically have vey low pemeabilities, which effectively impede vetical leakage to o fom ovelying o undelying wate souces. Howeve, vetical factues and faults ae widespead and povide pathways fo the movement of wate between stata. The San Antonio Region of the Edwads Aquife is bounded on the noth by the up-dip limits of its suface outcop; 6 7 A map showing the coss-section locations pesented in Figues 2.2A though 2.2c is contained in Appendix A. Stike of a fault - The diection in which a fault line is oientated with espect to tue noth. -6

11 =="'j., =="'j 1-t...J FEET oo t- = 4oo L oo 1 1 SEA j LEVEL t,fb.,...: o" :s "''ti,.....,o.:.. fb,..., fbfb ',..,.., l 11l,.. 2 EXPLAATON : OEOLOOC UNTS 1 J 4 Ka Anacacho llm.. tone (lnclud.. younge 'f 1 fomation n aome aeu) 8 Kau Auatln OtOU l 8 Kebd Eagle Fo Goup, Budl! Llmeatone, 1nd Del Rio Clay 1 Ka Edwlda Goup of Roea (1g72),undltta- 1 entllted 1nd ovelying Geogetown Fon1tlon t -...,fb a" a "',; "',;._a,,,./"... o... o S' tt{,lb,. fb,-v,-v tt{,. l" ',') ')'\ q{,fb.,.. a".,..,o tt{..,ts (,) a" Paaon Fomation of Edwltda Goup of R11 ( tg72), lncludal Geogetown Fomation Kilne Fom tloft of Edwad OOU of Roaa (1872) Olen Ro.. Fon1t1on Uncllld olde fonatioftl n aoma ae.. ) CONFNNO EDS EDWARDS AQUFER t t W.E i t t ltii.owt VJ'TCAL CAU OMA'n.Y XAOOAATD Kg FAULT-Aow allow diection of movamen1 Figue 2.2B NOTE: Fot' looatlon of ctlon N ftoua 1 Hydogeologic Coss-Section fo Section G-G' (Souce: USGS 1985)

12 zz ZZ' H C'J FEET f-- 1 8,_ SEA LEVEL GEOLOGC UNTS Ka Kau Kv Kabd Kg EXPLANATON Anacacho Llmaotonu Uncludaa younge fomations n eome aeae) Auetln Goup Volcanics Eagle Fod Goup, BuCia Limestone, and Dol Alo Clay Ka. Salmon Peak Fomation of Lozo and Smllh ( 1884) Km McKnight Fomation of Lozo and Smith ( 1884) Kw Weal Nuacoa Fomation of Lozo ana Smith ( t 884) Kg D Olen Roao Fomation (ncludes olde fomatlona n aoma aeas) CONFNNG BEDS EDWARDS AQUFER FAUL T--Aowa ehow diection of movement,'b.j..q Kg..... ;'\ otb..... '}; q{.j..q"" '}; land,".j..q._q; q{,'b t 3 4 ULE t KLOUETER VERTCAL SCALE OREA TL Y E XAOOERATED OJ, c{q; }o (b(b.j..q'!),.. 'JJO.. c{ c{,cb o OJ, t(., q{,v q"" z;, 4: 4. q'".j..q)btb C?i L--NOTE:F-o-locallo-n_of- ctlon eflguot jl 14 Figue 2.2c Hydogeologic Coss-Section fo Section ZZ-ZZ' (Souce: USGS 1988)

13 ,a-a (6L.6t uo1oas -amo.l :ao.:tnos) OlDOto.:tp.hqoaf) 1 OOU -- GOA - - l i -COO COl..._,... Meay, l... "......,.,...,... El - t J.. oot! '1 -- H ' 1 411,... K1W$ 1 oo t--t , " '.., t. - _.....,_......,._, ""-s --s _.,.os.,..."'- -- U Dtl "'..,.....,....,t i H + 1-t +- --'to o-..--'-'""...,,... ",....,s. c t... t---.,--all l---1 -tt-- t-" t -H-... t--t ,.,......,, '"... t--t -_,_ C

14 H... ;t;(p L..L...J-..._... ""....,. -- " - - l---"'1.. "ti-n1--...;..... )! ::.i i Figue 2.4 Geohydoloqic Section D-D' (Souce: TDWR 1979)

15 ---w1 i=jl 4' ){,.L_ o 'L-.:, KMBLE :-) K[RR '9-.:t.\n BLANCO.1:.-f -f;.... ' 8' / 29'!'- W Km NEv---...,. H Bett 11 e.. : ---;;:l-..-lj lite, LeoM Spln":. _ ' > Z'AVA ; 29'- + + i..... CQ to t----,---l to ao ULEB 1 <LOYETEAS + EXPLANATON RECHARGE AREA--Modified fom Puente, 1 9 qoundary OF FRESHWATER PART OF EDWARDS AQUFER UNE SEPARATNG UNCONFNED ZONE TO Tt' NORTH FROM THE CONFNED ZONE TO THE SOUTH,.M..Y UNDARY OF DRANAGE DVDE Loutlon map Figue 2.5 Location of the San physiogaphic egions, contibute to echage. (Souce: USGS 1986) Antonio, Edwads Aquife, and dainage basins that NOTE: 8alcon.. Euapment eepeetee the Edwad Pia tea f- the Gulf Coutel Plain, Catchment aea lea wh tim Edwad Plateau and tekll aufaca -" to ateama that co11 the echage aea of the Edwad acfle "' the San Antonio egion

16 '. on the west in Kinney County and in the east in Hays county by gound wate "highs"; and on the south by the "bad-wate" line. Both unconfined 8 and confined 9 aquife conditions exist within the Edwads Aquife. The unconfined potion is located in the nothen aea of the Aquife, whee the Edwads and Associated Limestones outcop at the suface in the Rechage Zone (see Figue 2. 5) Within this potion, gound wate is unde wate table o fee suface conditions. The confined potion of the Aquife occus downdip of the echage zone and extends southwad to the bad-wate line (see Figue 2. 5). Within this aea, goundwate is unde atesianw o "pessue" conditions, since it is confined undeneath the Del Rio Clay. The Edwads Aquife can be chaacteized as an undegound stoage esevoi, simila in natue to othe egional subsuface fomations such as the Caizo-Wilcox Aquife, Tinity Aquife, Ogallala Aquife, and Gulf Coast Aquife. Like othe majo goundwate fomations, the Edwads Aquife eceives suface wate echage and flow within the fomation is diffused and highly influenced by baie faults and geologic featues. Also like othe majo goundwate fomations, The Edwads Aquife is used fo beneficial puposes, via well pumpage, and has natual dischage points (spings). 8 Unconfined aquife - uppe bounday. An aquife in which the wate table foms the 9 1 Confined aquife - An aquife contained between two ock o othe estictive stata that etad but do not pevent the flow of wate to o fom an adjacent aquife. Atesian aquife - An aquife which. is ovelain (confined) by an impemeable laye so that the wate is unde hydostatic pessue. The wate level in an atesian well will ise above the top of the aquife to the level of the piezometic suface; howeve, the well may o may not flow at the land suface. -12

17 t 3. Rechage Zone: San Antonio Region of the Edwads Aquife Rechage to the Edwads Aquife occus within the outcop aea (echage zone) of the Edwads and Associated Limestones (see Figue 2.5), whee wate quickly seeps fom oveland flow, steams, ceeks, and ives. All majo watecouses in the egion, with the possible exception of the Guadalupe Rive whee the potentiometic head in the Edwads Aquife is highe than the elevation of the ive, lose wate to the Edwads Aquife as they tavese echage zone. The echage to the Edwads Aquife is deived mainly fom seepage and infiltation fom steams that coss the outcop of the Aquife and fom diect infiltation of pecipitation on the outcop. Appoximately 85% of the echage (USGS 1986) is fom the infiltation of steamflow whee steams coss the outcop aea. Most of the emainde of the echage is by pecipitation on the outcop. Additional echage occus to the Edwads Aquife as coss-fomational flow fom the Glen Rose Fomation paticulaly whee this fomation is placed togethe against the Edwads by faulting (USGS 1986). The westen pat of the echage zone is compised of the Fio Sabinal, the Nueces, and the Seco-Hondo-Medina Rive Basins that collectively have about 6 pecent of the total catchment aea but supplies about 7 pecent of the total echage to the Aquife (about 2, 9 5o sq. mi. ) The emaining 3 pecent of the echage is deived fom the easten potion of the echage zone which includes the San Antonio and Guadalupe Rive basins (EUWD 1988), excluding the Guadalupe Rive. Rechage wate, oiginating fom suface souces, entes the unconfined zone of the Aquife. Gound wate then flows (by gavity) downndip towad the confined potion of the Aquife whee -13

18 . the wate moves to the east and notheast though the atesian zone (confined zone) towads the aeas of natual dischage. Majo spings that dischage wate fom the San Antonio Region of the Edwads Aquife include Leona Spings nea Uvalde, San Antonio and San Pedo Spings in san Antonio, Comal Spings at New Baunfels, and San Macos Spings at San Macos. n addition, wate is pumped fom the Aquife by thousands of wells located in Kinney, Uvalde, Medina, Bexa, Comal, and Hays Counties. 4. Atesian Zone: San Antonio Region of the Edwads Aquife The confined o atesian potion of the Aquife occus downdip of the echage zone and extends to the bad-wate line. Gound wate moving fom the unconfined echage zone moves down-gadient into the deepe o confined (atesian) zone of the Aquife. The flow of gound wate (USGS 1986) within the Aquife (unconfined and confined zones) is pofoundly influenced by the pesence of faults (Figue 4.1). Faults ceate extemely anisotopic 11 conditions, acting both as baies to flow and as conduits fo lateal and vetical flow. Displacement of highly pemeable beds opposite impemeable beds causes flow to be diveted lateally, paallel to the stike of the faults. Disuption of flow paths in the Aquife by faulting esults in fault blocks with flow systems which ae sepaate fom the main flow systems of the Aquife. The stuctual complexity of the San Antonio Region effects wate movement in both the confined and unconfined potions of the Aquife. Reseaches (Maclay and Small 1986) have found that in the atesian zone the hydaulic gadients ae elatively flat and 11 Anisotopic An aquife is anisotopic if the hydaulic conductivity vaies with the diection of measuement at a point within the aquife. -14

19 ...--, --=w too-so 1o-oo... ao w. )! n.,--_j !']- > fi<nncy /,';\! UVALDE i i ao - + tn ["... ) ' oo ,,.oo to 1 1 MLU to to 1 KLOMU:R..../o+., ' +...<_':' ' (jj + EXPLANATON RCHARGE AREA-Modified fom Puente, BOUNDARY OF FRESHWATER PART OF EDWARDS AQUFER LNE SEPARATNG UNCONFNED ZONE TO Ttil NORTH FROM THE CONFNED ZONE TO TH: SOUTH, JULY f-fault--u, upthown, D, downthown. Oaahed whee nfeed LOCATON OF GEOLOGCAL STRUCTURE Figue 4.1 Majo Faults (Souce: TDWR 1979)

20 tansmissivities 12 ae vey lage when compaed to the unconfined (echage) zone. Aquife tansmissivity values ae difficult to quantify, due to the natue and egional chaacteistics (poosity and pemeability) of the Aquife. An estimate of tansmissivities was calculated by Maclay and Small (1986) to be extemely high, anging fom 2, sq ft pe day to 2 million sq ft pe day. Specific yields 13 and stoage coefficients 14 have also been estimated fom pevious wok on the Edwads Aquife. Maclay and Small (1986) estimated the stoage coefficient to ange fom about.1 to.1 within a specified yield of 3 pecent. Klemt and othes (1979) detemined stoage coefficients anging fom.4 to.8, with estimated specific yields of 6 pecent. The extemely high tansmissivity of the atesian zone of the Edwads Aquife is indicated by (1) vey low hydaulic gadients, (2) excellent coelation of wate levels among widely spaced wells, (3) lage sustained spingflows, and (4) unifom quality and tempeatue of wate within the Aquife (USGS 1986). This capacity to tansmit lage quantities of wate is indicated by the pesence of hundeds of wells, some of which poduce thousands of gallons of wate pe minute with the esulting dawdown in wate levels of only a few feet. Reseaches (Maclay , Knowles 199) have pojected a wide Tansmissivity - The ate at which wate is tansmitted though a unit width of an aquife unde a unit hydaulic gadient. Specific yield - The quantity of wate that an aquife will yield by gavity if it is fist satuated and then allowed to dain; the atio expessed in pecentage of the volume of wate dained to volume of the aquife that is dained. Stoage coefficient o coefficient of stoage - A measue of the volume of wate available fo withdawal and is defined as the volume of wate eleased fom o taken into stoage pe unit suface aea of the aquife pe unit change in the component of head nomal to that suface. -16

21 vaiance in the estimated wate stoage capacity of the Aquife. Estimates ange fom 25 million af to 55 million af of wate. Of this quantity, it is estimated that 1.5 million af of wate can be t L stoed in the Aquife above the invet elevation (666 ft msl) of Comal Spings. Also, it is estimated that each one foot of the Aquife epesents an aveage of about 25, to 5, af of wate stoage (Maclay 199). 5. Goundwate Stoage Stoage in a satuated confined aquife is defined as the volume of wate that the Aquife eleases fom stoage pe unit suface aea of the Aquife pe unit decline in the hydaulic head. As the pessue in the Aquife is educed such as by pumping wate fom a well and yielding wate, changes in pessue in a confined aquife poduce only vey small changes in the volume available fo the stoage of wate. n the unconfined pats of the Aquife, the level of satuation changes as the wate table moves up and down. The amount of wate that the unconfined aquife yields is the amount of wate that will dain fom the poe spaces. Thee is no compession of the Aquife famewok involved and the volume of wate yielded fom a given volume of aquife ock, unde unconfined conditions, is as much as five odes of magnitude geate than fo an equivalent volume of ock unde confined conditions (Patteson 1991). Wate stoed between the histoical ange in wate levels in the Edwads Aquife is contained pimaily within the unconfined zone (USGS 1986). Changes in wate levels in the unconfined zone epesent significant changes in the volume of wate stoed in the Aquife, as compaed to changes in wate levels within the confined zone epesent only vey small changes in volume of wate stoed within the Aquife. Because the aea of the unconfined zone -17

22 epesents a significant pat of the Aquife, a vey lage pecentage of the wate eleased fom stoage fo the histoical ange in wate levels comes fom this zone. The quantity of wate tempoaily stoed with the unconfined zone between echage events is affected stongly by geologic stuctue (USGS 1986). A system of paallel faults ae oiented in a manne to obstuct the flow of gound wate fom the unconfined zone to the confined zone (Figue 5.1). This esults in vey slow wate movement fom the unconfined zone to the confined zone, thus causing the quantity of wate in stoage in the unconfined zone to emain fo longe peiods. As the wate table dops in the unconfined pat of the Aquife, sections of the Aquife in the echage zone may be dewateed. Futhe declines in the wate table could cause confined pats of the Aquife to come unde unconfined conditions, with a esulting change in stoage capacity. The volume of the atesian o confined zone epesents 3-4 pecent of the total volume of the Aquife. Theefoe, a vey lage amount of wate eleased fom the Aquife comes fom stoage (i.e. 6-7 pecent) in the unconfined zone. The quantity of wate etained in the atesian (confined) zone afte a echage event is affected stongly by the geologic stuctue of the Aquife. Faults can act as baies to educe the flow of wate moving fom the unconfined zone to the atesian zone, theeby allowing a geate volume of wate to emain in the unconfined zone fo a longe peiod of time and with a slow loweing of wate levels. Based on an analyses of the faulting system, wate levels and modeling of genealized goundwate movement in the Aquife, the USGS (1986) segmented o divided the unconfined zone of the San Antonio Region into the following fou distinct aeas o pools (Figue 5.2): Westen Stoage Unit: This unit lies in Kinney and Uvalde County and includes the unconfined zone west of the Woodwad Cave Fault -18

23 1---cj} -='jj =-<=J "9 e.-oo OO"ao oo oo ao oo ao-ao - W fi!--- : N(Y + - H... \D... -oo EXPLANATON ECHARGE AREA-Modified fom Puente, 1 1 ao UfLEa 1 ao ao LOMTS BOUNDARY OF FRESHWATER PART OF DWARDS AQUFER UNE SEPARATHG UNCONFNED ZONE TO TH jcorth FROM THE CONFNED ZONE TO TH!sOUTH,.M..Y 1874 ;-- FAUL T--u, uptht'own: D. downchown. Daahe,whoe nfeed Figue 5.1 Locations of selected geologic stuctues esticting and conveying gound wate. (Souce: TDWR 1979)

24 m< R""'1J ""i"' H "'......" w ) n--...l_ - ---!K. fi(nn(y.1',;.\! UVAlDt i... _ i J "'- ) -... _ fmaydieit t--'"iaym.t' e tl 1e CROMU'Cal + +- EXPLANATON ( RECHARGE AREA-Modified to<!! Puoftl BOUNDARY OF FRESHWATER PART OF EDWARDS AOUFER LNE SEPARATNG UNCONFNED ZONE T NORTH FROM THE CONFNED ZONE TO SOUTH, JULY BOUNDARY Ga'ARATHG STORAGE ANO u. -o FAULT,...,o-. D, ciowftl"'o-. o...,.....s Figue 5.2 Stoage extenal (Souce: and flow units boundaies. TDWR 1979) and aeas of flow acoss

25 and the complex of faults in the Uvalde aea that is an extension of the Medina Lake Fault. The Easten limit is the topogaphic divide between Sabinal Rive and Seco Ceek, located in easten Uvalde County and westen Medina County. Most of the echage comes fom losses of flow in the Nueces, West Nueces, Fio, Dy Fio, and Sabinal Rives. This unit has the lagest stoage capacity of the fou unconfined units and is the most emote fom the majo dischage points. Westen Medina Stoage Unit: This unit includes the unconfined zone between the westen stoage unit and the Medina Lake Fault. Most of the echage comes fom Hondo and Seco Ceeks and fom Medina Lake. Easten Medina Stoage Unit: This unit includes the unconfined zone between the westen-medina stoage unit and geneally along the Haby Cossing Fault. The unit eceives most of its echage fom the Medina Rive, Medina Lake and seveal-small aea ceeks. Easten stoage Unit: This unit includes the unconfined zone east of the easten-medina stoage unit. ts stoage is stongly influenced by the nothen Bexa County Fault and the Hueco Spings Fault. The echage is pimaily fom seveal small-aea steams, especially Cibolo Ceek. 6. Goundwate Movement The USGS (1986) pefomed extensive studies to evaluate and detemine goundwate movement within the Edwads Aquife. n the 1986 study, the USGS defined flow units as an aea of the Aquife that includes a stoage unit and a zone tha tansmits wate fom the stoage unit to majo points of dischage (i.e., wells and -21

26 spings). Based on the USGS study, fou flow units wee defined (see Figue 5.2): Westen-southen Flow Unit: The souce of wate fo this flow unit is the Westen stoage Unit. Due to Aquife geomety, wate moves though this flow unit taking the southenmost oute fom the aea of echage to points of dischage that extend to Comal Spings. Fo the most pat, wate moves though the westen pat of an opening (Knippa Gap) in the Medina Lake Fault-Uvalde Host 15 complex nea Sabinal and a gaben 16 in the Uvalde aea. Most o all of this flow is withdawal by iigation wells in Medina County and by the City of San Antonio. South-Cental Flow Unit: The souce of wate fo this unit is the Westen Medina Stoage Unit. Within this flow unit, the Medina Lake Fault functions as a majo baie of goundwate flow and divets the wate to the southwest and moves though the easten pat of the Knippa Gap nea Sabinal that is descibed above. Afte the wate moves past the opening it tuns shaply to the east. The majo dischage points ae iigation wells in Medina County and municipal wells in San Antonio and Comal Spings. Noth-Cental Flow Unit: The Easten Medina Stoage Unit povides the souce of wate to the Noth-Cental Flow Unit. Much of the flow is diveted to the southwest by the Haby Cossing Fault befoe tuning eastwad. Majo dischage points ae municipal wells in San Antonio and Comal and San Macos Spings. This flow unit meges with the two southen (i.e. Westen-Southen and South Cental) flow units at Comal Spings. Easten Flow Unit: The souce of wate fo this unit is the S Hos - A aised ock mass located between two faults. 16 Gaben - A loweed ock mass located between two faults. -22

27 easten stoage unit. Wate in the westen pat of the unit is diveted to the southwest by baie faults, but in a shot distance tuns to the notheast. Duing nomal Aquife wate levels, most of the flow fom this unit dischages at San Macos Spings. Gound wate velocities in the Edwads Aquife have been estimated o measued by seveal diffeent methods (TWDB 1986) A goss estimate can be made fo the confined feshwate zone on the basis of the estimated total volume of wate stoed in the confined zone of the aquife. The TWDB (1986) estimates that the total volume of wate in the confined zone of the Edwads Aquife is 19.5 million ace-feet (TWDB 1986), and that the appoximate aveage annual echage is 55, ace-feet. Using these TWDB estimates, the esidence time fo wate in the confined zone is about 35-yeas (19,5, af 1 55, af). The TWDB also estimates that the aveage distance an incement of wate fom the confined aquife west of Comal Spings would tavel though the confined aquife to Comal Spings duing the 35 yeas is about 65 miles {TWDB 1986). Based on these values the estimated gound-wate velocity is about 27 ftlday {65 mix 5,28 ftlmi 35 ys 365 dly). Howeve, a moe ecent study pefomed by the Bueau of Economic Geology {BEG 1993), UT at Austin, in 1993, estimates that the confined zone contains appoximately million ace-feet of wate. Using this highe confined stoage volume estimate yields a esidence time fo wate of about yeas (156,5, af 55, af), and a gound-wate velocity of about 3.3 ftlday (65 mi x 5,28 ftlmi ys d/y) Both calculations stongly indicates that the Edwads Aquife is tuly chaacteistic of a gound wate fomation with flow though estictive poous media. As descibed above, the southen bounday of the confined potion of the Edwads Aquife is the "bad-wate" line. This line is set whee the concentation of 1, mgll (milligams pe lite) of dissolved solids occus in the Aquife. The concentations of -23

28 dissolved solids at given sampling points vay slightly with time, but the lateal position of the "bad-wate" line has not significantly shifted ove time (TWDB 1986). n addition, thee is no indication that the "bad-wate" line shifted significantly, even duing the 195's dought when Comal Spings went dy. The diffeence with wate quality between the bad wate zone and the fesh wate zone of the Edwads Aquife occus because thee is little o no ciculation of wate in the bad wate zone. Wate has esided in the bad wate zone fo such a length of time that mineals have dissolved fom the ocks in lage enough quantities to poduce high levels of dissolved solids. Given the extemely slow movement of wate within the bad wate zone, eduction in head of the in the fesh wate zone should nomally esult in only mino and localized inflow of saline wate. n geneal, the aquife in the saline-wate zone (i.e. bad wate zone) has consideable less capacity to tansmit wate than the aquife in the feshwate zone because an integated netwok of cavenous zones has not be developed by ciculation of feshwate. As a compaison, the tansmissivity of the saline wate zone (668 ft 2 /d) is 2 times less than the tansmissivity of the feshwate zone (134, ft 2 /d) fo the feshwate zone (USGS 1986). n addition, faults significantly disupt the lateal continuity of the geologic fomations at places in Bexa county, impeding o peventing flow in faulted aeas. These factos seve to estict lateal gound wate flow acoss the "bad-wate line. This is futhe confimed by an examination of Aquife coss-sections which tansect the confined and "bad-wate" zones. Appoximately 3 such coss-sections wee pepaed by T. A. Small (USGS 1986). The USGS (1986) found that some undetemined amount (but elatively small due to low hydaulic gadients and low saline-wate zone tansmissivities) flow pobably moves fom the feshwate to the saline wate pat of the aquife in Kinney, Uvalde and westen Medina Counties and fom the saline-wate to feshwate pat of the -24

29 ... aquife in Hays and Tavis Counties. t should be noted that fo puposes of mathematical modeling, the TWDB teats the "bad-wate" line as an impemeable aquife bounday, with the exception of a small aea in southeast Uvalde County. Based on a eview of the liteatue and vaious mathematical modeling studies, egional Edwads Aquife wate quality degadation will not occu as a esult of updip movement of the "bad-wate" line. This line has limited oppotunity fo updip movement and if it does move up-dip due to exteme conditions in the fesh wate zone, its movement will be vey limited, not causing a theat to egional wate quality. The Edwads Aquife also has some limited hydologic communication with the undelying and "pooe" wate quality Glen Rose Aquife {EUWD 1995). Because of faulting, the Edwads Aquife in many aeas ove the 18-mile length between the two gound-wate divides is juxtaposed 17 to the Glen Rose Aquife. Both at the suface and a depth, and theefoe, the Glen Rose may dischage diectly into the Edwads Aquife. Regionally, undeflow fom the Glen Rose Fomation to the Edwads Aquife along the Balcones fault zone can occu by gound wate moving lateally in a down-gadient diection within the Glen Rose and enteing the Edwads aquife though fault planes. The amount of gound wate in tansit is dependent on the length of the line of enty (fault plane) though which wate entes the Edwads Aquife, the wate level gadient acoss the fault plane fom the Glen Rose to the Edwads Aquife, and the effective tansmissivity fo the Glen Rose Aquife upgadient and along this line. The EUWD {1995) estimates that the appoximate ange of total Glen Rose undeflow to the Edwads Aquife would be about 2,7 to about 11,4 af/y in the San Antonio Region. As compaed to the total Edwads Aquife wate balance, these 17 Juxtaposed - othe. Fomations o stata that lie next to o abut each -25

30 L estimates indicate that the Glen Rose contibutes less than 2 pecent of the total wate budget duing aveage echage conditions. The EUWD (1995) also estimated that, based on geochemical models, the chemical content of wate epesentative of the Edwads Aquife in the San Antonio Region include a small amount, less than 1 pecent Glen Rose wate (EUWD 1995). Thus, local communication between the fomations occus, but without significant impact on oveall wate quality of the Edwads Aquife, due to the low tansmissivity of the Glen Rose. l 7. Histoical Rechage Table 7.1 lists the estimated histoical annual echage (USGS 1995) to the Edwads Aquife fom 1934 to 1991 and is pesented in Figue 7.1. Estimated annual histoical echage fo the Aquife vaied fom 43,35 af in 1956 to 2,63,986 af in The aveage annual histoical echage fo this peiod was 676,666 af. Annual echage by Edwads Aquife Stoage Unit, as identified above, is pesented in Table 7.2 and shown in Figue 7.2. Fo the 1934 though 1994 peiod of ecod, echage fo the Westen Stoage Unit, which eceives inflow fom the Nueces, Fio and Sabinal Rive Basins, aveaged 34,49 affy. Rechage to the Westen Medina stoage Unit aveaged 162,267 affy fo the same peiod. This stoage unit eceives inflow fom the Seco and Hondo Ceek Basins and fom Medina Lake (USGS 1986). The Easten Medina Stoage Unit eceived an aveage echage fom the Medina-Cibolo Ceek Aea of 67,466 af/y fo the 1934 though 1991 peiod. Rechage to the Easten Stoage Unit, which eceives echage fom Cibolo and Comal Ceek Basins, aveaged 13,64 af/y fo the same peiod. The Blanco Rive, which povides echage diectly to the San Macos Spings aea, had an aveage annual echage of 38,839 af/y. oveall the Westen Stoage Unit eceived 45 pecent of the -26

31 TABLE 7.1 TOTAL ANNUAL RECHARGE BY CONTRBUTNG WATERSHED TO THE EDWARDS AQUFER SAN ANTONO REGON (ACRE FEET/YEAR) (SOURCE: U.S. GEOLOGCAL SURVEY, 1995) YEAR NUECES FRO SABNAL SECO HOND MEDNA MEDNA CBOLO COMAL BLANCO TOTAL RVER RVER CREEK CREEK RVER CBOLO CREEK CREEK RVER ANNUAL BASN BASN BASN BASNS BASN CR. AREA BASN BASN BASN RECHARGE ,6 27,91 11,844 19,92 46,5 21, 11,844 16,555 19, , ,31 192, , ,21 71,1 138,21 136,861 45,841 39,8 1,338, ,49 157,39 129,m 142,899 91,6 18, ,m 16,325 42,72 995, ,8 75,69 49,396 61,299 8,4 47,8 49,396 14,53 21,2 428, ,52 69,278 34,74 54,1 65,5 46,2 34,74 42,12 36,4 446, , 49,55 7,546 33,1 42,4 9,33 7,546 2,59 11,1 389, ,4 6,313 27,418 56,6 38,8 29,299 27,418 3,383 18,81 312, ,9 151, , ,999 54,1 116,3 142,692 48,59 57, , ,5 95,91 61,36 84,4 51,7 66,9 61,36 32,24 28,6 585,151 1-t ,5 42,31 35,96 33,8 41,5 29,5 35,96 23,21 2,99 297, ,19 75,967 9,983 74,33 5,5 72,5 9,983 61,515 46,21 627,61 N ,3 71,86 89,355 78,62 54,8 79,599 89,355 4,546 35,71 586, ,9 54,215 9,179 51,999 51,4 15,1 9,179 65,122 4, , ,4 n,67 55,543 45,2 44, 55,498 55,543 23,961 31,6 461, ,1 25,66 13,846 2,2 14,8 17,51 13,846 6,57 13,2 166, , 86,134 32,9 7,3 33, 41,8 32,9 23,89 23,5 58, ,5 35,496 16,444 27, 23,6 17,298 16,444 8,161 17,4 23, ,3 28,412 1,924 26,4 21,1 15,3 1,924 1,579 1,6 134, ,9 15,695 91,284 3,2 25,4 5,1 91,284 11,17 2,7 363, ,4 15,18 2,837 4,4 36,2 2,11 2,837 21,467 24,9 185, ,324 31,6 5,4 11,9 25,3 4,19 5,4 4,6 1,7 16, ,972 22,1 3, 7,7 16,5 4,29 3, 3 9,5 194, ,6 4,2 1,2 3,6 6,35 2, 1,2 1, 8,2 43, ,6 133,6 252,9 129,52 55,6 175, ,9 145, 76,5 1,33, ,7 3, 21, 294,9 95,5 19,91 21, 67,7 7,72 1,688, ,6 158,9 49,8 96,7 94,7 57,354 49,8 28,1 33,6 678, ,7 128,1 11,6 126,98 14, 89,741 11,6 58,5 62,4 861, ,2 151,3 69,6 15,4 88,3 69,3 69,6 41,2 49,4 729, ,4 46,6 15,7 23,499 57,3 16,7 15,7 9, 18,9 25, ,7 27, 11,5 1,3 41,9 9,3 11,5 9,8 16,2 1n,2oo ,1 57,1 32,4 61,3 43,3 35,8 32,4 18,7 22,2 429, ,899 83, 63,2 14, 54,6 78,8 63,2 52,1 66,7 663,499

32 f""'"j -"'"j =:"1J -"'"j,, ----ij.---, --=J TABLE 7.1 -CONTNUED TOTAL ANNUAL RECHARGE BY CONTRBUTNG WATERSHED TO THE EDWARDS AQUFER - SAN ANTONO REGON (ACRE-FEET/YEAR) (SOURCE: U.S. GEOLOGCAL SURVEY, 1995) YEAR NUECES FRO SABNAL SECO HOND MEDNA MEDNA- CBOLO COMAL BLANCO TOTAL RVER RVER CREEK CREEK RVER CBOLO CREEK CREEK RVER ANNUAL BASN BASN BASN BASNS BASN CR. AREA BASN BASN BASN RECHARGE ,2 134, 35,9 78,2 5,5 44,5 35,9 3,616 34,6 613, , ,9 3,48 64,8 44,65 3,2 3,48 26,8 19, 466, , , 73,2 198,67 59,9 83,1 73,2 47,4 49,3 891, , ,8 57,7 84,23 55,4 6,2 57,7 42,2 46,6 637, , ,9 64,866 81,61 68, 68,8 64,866 48,933 39,5 691, ,4 212,4 46, ,57 68,7 81,4 46,968 35,432 22,2 933, ,4 144,6 59, ,59 87,9 74,31 59,394 44,86 33,4 766,794 H ,6 256,9 12, ,38 97,6 237,195 12,669 91,31 82,2 1,483, ,12 135,64 43, ,258 96,2 68,116 43,846 33,78 39,9 666, , , , ,943 93,45 138, ,446 68,284 85,866 1,52, ,78 238,551 46, ,98 94,5 47,932 46,637 7,622 57,89 872, , ,964 99,8 159,494 77,735 97,922 99,8 92,568 66, , ,863 73,144 3,637 13,66 76,7 49,547 3,637 41,835 26,272 52, ,431 21, ,596 23,95 89,4 85,37 152, ,696 75,22 1,21, ,64 85,616 17,392 25,319 88,3 18,771 17,392 37,784 31, , ,46 365,18 128,95 252,19 91,3 164, ,95 68,728 67,33 1,47, , ,367 29,463 9,919 76,8 22,589 29,463 15,395 23,461 43, ,194 85,98 34,279 42,894 74,35 31,885 34,279 28,258 23, , ,421 4,425 9,754 18,12 43,9 11,316 9,754 7,112 25,97 198,m , ,936 15, ,538 64,7 136,737 15,956 18,236 5,691 1,13, , , , ,583 74,75 17, ,289 16,65 44,472 1,272, ,57 473, ,22 45,527 9, , ,22 99, ,874 2,63, , ,934 11,313 24,878 69,99 12,586 11,313 17,84 25, , ,577 52,645 3,523 13,497 46,867 4,562 3,523 8,795 23,565 29, , ,38 39, ,222 53,989 35,934 39,136 32,662 41,283 1,17, , ,9 57, ,25 52,8 84,477 57,743 51,967 96,939 1,463, ANNUAL AVERAGE 114, ,6 64,652 11,742 6,525 67,466 64,652 38,953 38, ,

33 , -,l lfl-,!"",,", FGURE 7.1 GRAPH OF ANNUAL RECHARGE TO THE EDWARDS AQUFER - SAN ANTONO REGON FOR 1934 THROUGH 1991 RECHARGE (THOUSAND ACRE-FEET} 2,5 [ o.:...:::::...: , 1-1 1,5,J \ 1, f 5 Q! 1-, )---1 -,-- 1,..,.., '.,... T'::T: t t-: t.:t:::-j;_,-j.::.j:.::t:::.t:.::t --1 1! 1 Mq«QUUNMMUYaMMVUUonnnnnHHHMHHVNU YEAR NCLUDES THE NUECES, FRO, SABNAL, SECO, HONDO, MEDNA, CBOLO, COMAL, AND BLANCO WATERSHEDS SOURCE: U.S. GEOLOGCAL SURVEY, 1995

34 TABLE 7.2 TOTAL ANNUAL RECHARGE BY CONTRBUTNG FLOW UNT TO THE EDWARDS AQUFER - SAN ANTONO REGON (ACRE-FEET/YEAR) (SOURCE: u.s. GEOLOGCAL SURVEY, 1995) UNT YEAR WESTERN WESTERN EASTERN EASTERN BLANCO TOTAL STORAGE MEDNA MEDNA STORAGE RVER ANNUAL ST. UNT ST. UNT UNT BASN RECHARGE ,345 66,42 21, 28,399 19, , , ,31 138,21 182,72 39,8 1,338, , ,499 18, ,98 42,72 995, , ,699 47,8 63,899 21,2 428, ,52 119,6 46,2 76,86 36,4 446, ,51 75,5 9,33 9,65 11,1 389, ,131 95,4 29,299 3,81 18,81 312, , ,99 116,3 191,21 57, , , ,1 66,9 93,6 28,6 585, ,96 75,3 29,5 58,36 2,99 297, ,59 124,83 72,5 152,498 46,21 627, , ,42 79, ,91 35,71 586, ,294 13,399 15,1 155,31 4, ,793 25,613 89,2 55,498 79,54 31,6 461, ,552 35, 17,51 19,93 13,2 166, ,224 13,3 41,8 55,899 23,5 58, ,44 5,6 17,298 24,65 17,4 23, ,636 47,5 15,3 12,53 1,6 134, ,879 55,6 5,1 12,31 2,7 363, ,345 4,6 2,11 42,34 24,9 185,25 98,324 37,2 4,19 1, 1,7 16, ,72 24,2 4,29 3,3 9,5 194, , 9,95 2, 2,2 8,2 43, ,1 185,12 175, ,9 76,5 1,33, ,7 39,4 19,91 268,7 7,72 1,688, ,3 191,4 57,354 77,9 33,6 678, ,4 23,98 89,741 16,1 62,4 861, ,1 193,7 69,3 11,8 49,4 729, ,7 8,799 16,7 24,7 18,9 25, ,2 52,2 9,3 21,3 16,2 177, ,6 14,6 35,8 51,1 22,2 429, ,99 158,6 78,8 115,3 66,7 663,499-3

35 TABLE CONTNUED TOTAL ANNUAL RECHARGE BY CONTRBUTNG FLOW UNT TO THE EDWARDS AQUFER - SAN ANTONO REGON (ACRE-FEET/YEAR) (SOURCE: U.S. GEOLOGCAL SURVEY, 1995) YEAR WESTERN WESTERN EASTERN EASTERN BLANCO TOTAL STORAGE MEDNA MEDNA STORAGE RVER ANNUAL UNT ST. UNT ST. UNT UNT BASN RECHARGE ,1 128,7 44,5 66,516 34,6 613, ,615 19,45 3,2 57,28 19, 466, , ,57 83,1 12,6 49,3 891, , ,63 6,2 99,9 46,6 637, , ,61 68,8 113,799 39,5 691, , ,27 81,4 82,4 22,2 933, , ,49 74,31 14,2 33,4 766, , ,98 237, ,7 82,2 1,483, ,66 211,458 68,116 76,924 39,9 666, , , , ,73 85,866 1,52, , ,48 47,932 54,259 57,89 872, , ,229 97, ,576 66, , ,644 18,36 49,547 72,472 26,272 52, , ,495 85,37 266,292 75,22 1,21, , ,619 18,771 55,176 31, , , ,49 164, ,823 67,33 1,47, , ,719 22,589 44,858 23,461 43, , ,244 31,885 62,537 23, , ,6 62,2 11,316 16,866 25,97 198, , , , ,192 5,691 1,13_, , ,288 17, ,354 44,472 1,272, , , ,339 27, ,874 2,63, ,48 94,787 12,586 28,397 25, , ,745 6,364 4,562 12,318 23,565 29, , ,211 35,934 71,798 41,283 1,17, ,97 368,5 84,477 19,71 96,939 1,463, ANNUAL AVERAGE 34,49 162,267 67,466 13,64 38, ,

36 =, '""""'"']! '....'!! """''""'',...,.,',''"il FGURE 7.2 GRAPH OF ANNUAL RECHARGE BY STORAGE UNT TO THE EDWARDS AQUFER- SAN ANTONO REGON FOR 1934 THROUGH 1991 RECHARGE (THOUSAND ACRE FEET) - ''""''"''"""'"'' : ;,,.,,,,,,,,,,, : :':.,...,,,,.,.:...,...,,,.,,,.,...,...,..,..,_,,,,,;;j WilT..U. +w. EDNA.U. *' DNA t.u,.at,,u. )(.LANCO!Will H w l\j YEAR WTH TOAO UNT NCWO NUC, 1'111 AND -UlNA\. W ANt: WTH DHA TOAG l.lftt NCW) CO, HOHOO AN) UDHA LAitl: ATEA UDHA TOAO UHT NCWD DHA-CO.O Cll. AlitA: AN) ATH TOAO UNT NCW) CO.O AND COUA Cl'lll( Atl..AHCO. CHAAO AN ACO P.

37 histoical annual echage to the Edwads Aquife fo the 1934 though 1991 peiod of ecod. Howeve, most of the flow to and fom this stoage unit is used fo iigation and municipal puposes. 8. ffistoical Pumpage Sping Flows The estimated total histoical dischage (pumpage) fom wells and spings in the Edwads Aquife fo 1934 though 1991 is shown in Table 8.1. The annual histoical pumpage (EUWD 1992) fom the Edwads Aquife vaied fom 11,9 af in 1934 to 542,4 af in The aveage annual histoical pumpage fo this peiod was 284,81 af. The pumpage data shown in Table 8.1 is fo iigation, municipal and industial withdawals fom the Edwads Aquife within Kinney, Uvalde, Medina, Bexa, Comal, and Hays counties. n 1983, thee wee about 8 majo wells poducing wate fo the Edwads Aquife fo public wate supply (municipal), industial and iigation puposes (SWTSU 1988). n 1991, thee was an estimated 1, 354 majo wells located in the five counties ovelying the Edwads Aquife, as shown in Table These majo wells ae geneally distibuted ove the Edwads Aquife as shown in Fique 8.1. Majo well clustes ae located in Uvalde County and easten Medina County. Howeve, the lagest concentation of wells is located in Bexa, Comal and Hays Counties. Most of the wells used fo iigation puposes ae located in Uvalde County and to a lesse extent in Medina County. Howeve, most of the majo wells located in Bexa, Comal and Hays Counties ae used fo municipal (public wate supply) and industial puposes. Besides these majo wells, thee was an estimated 3,5 additional wells that have been located o geneally located by the TWDB (Stein 1993) within the five county egion that ae used fo domestic and livestock puposes. Howeve, thee ae numeous additional -33

38 TABLE YEAR 8.1 TOTAL ANNUAL PUKPAGE AND SPRNG FLOW DSCHARGE FROM THE EDWARDS AQUFER - SAN ANTONO REGON (ACRE-FEET/YEAR) PUMP AGE TOTAL CO MAL SAN MARCOS TOTAL MASS BALANCE SPRNG SPRNGS SPRNGS ANNUAL (RECHARGE - DSCHARGE RECHARGE PUMP AGE-TOTAL SPRNG DSCHARGE ,9 336, 23,155 KSSNG 183,944 (253,956) ,7 415,9 244,561 MSSNG 1,338, , ,7 485,5 265,171 MSSNG 995, , ,2 451, 259,18 MSSNG 428,484 (142,716) ,1 437,7 255,332 MSSNG 446,58 (111,292) ,9 313,9 217,84 KSSNG 389,559 (43,241) ,1 296,5 28,371 MSSNG 312,432 (14,168) ,8 464,4 26,632 MSSNG 942, , ,6 45,1 265,84 MSSNG 585,151 (9,549) ,1 39,2 246,597 MSSNG 297,111 (242,189) ,3 42,1 253,159 MSSNG 627,61 59, ,3 461,5 27,747 MSSNG 586,344 (28,456) , 428,9 276,23 MSSNG 629,793 45, , 426,5 257,827 MSSNG 461,415 (132,85) ,7 281,9 21,11 MSSNG 166,156 (284;444) ,4 3,4 211,958 MSSNG 58,723 28, ,8 272,9 189,631 MSSNG 23,343 (263,357) ,7 215,9 148,819 MSSNG 134,539 (291,61) ' ' ,4 29,5 162,366.MSSNG 363,58 (61;32) ,8 238,5 142,644 MSSNG 185,25 (283,5) ,2 178,1 98,314 MSSNG 16,414 (263,886) , 127,8 66,796 MSSNG 194,362 (194,438) ,1 69,8 27,991 MSSNG 43,35 (347,55) ,3 219,2 138,696 11,241 1,33, , ,3 398,2 234,16 153,391 1,688,412 1,7, ,5 384,5 229, ,12 678,554 59, ,1 428,3 241, , ,621 26, ,2 455,3 247, , ,3 45, ,9 321,1 193,333 95,832 25,799 (338,21) ,4 239,6 15,77 78, ,2 (338,8) ,2 213,8 138,515 7, ,3 (44,7) ,1 322,8 29, , ,499 84,

39 TABLE CONTNUED TOTAL ANNUAL PUMPAGE AND SPRNG FLOW DSCHARGE FROM THE EDWARDS AQUFER - SAN ANTONO REGON (ACRE-FEET/YEAR) YEAR PUMP AGE TOTAL CO MAL SAN MARCOS TOTAL MASS BALANCE SPRNG SPRNGS SPRNGS ANNUAL (RECHARGE - DSCHARGE RECHARGE PUMP AGE-TOTAL SPRNG DSCHARGE ,9 315,3 193,38 111, ,416 42, ,3 216,1 136,46 77, ,545 (9,855) ,7 48,3 246, ,13 891,58 231, ,5 351,2 212, , ,569 (21,131) ,4 397,7 226,58 144, ,87 (36,13) ,8 272,7 159,752 91,8 933,38 253, ,3 375,8 264, , ,794 19, ,4 527,6 293, ,158 1,483, , ,4 483,8 283, , ,194 (195,6) ,8 54,4 295,345 17,3 1,52, , ,5 53,9 28,33 153,16 872,457 19, ,6 58,3 289,61 161, ,39 27, ,8 375,5 239,88 87,394 52,295 (35,5) ,5 523, 292, ,889 1,21, , ,1 328,3 27,161 95, ,28 (438,372) ,1 47,3 234,395 13,955 1,47, , ,1 333,3 21,147 93,446 43,84 (355,596) ,5 31,6 171,989 16,23 434,274 (285,826) ,8 172,5 91,445 72, ,772 (53,528) ,5 334, 192,58 131,986 1,13,65 247, ,3 388,1 219,79 145,436 1,272,88 455, ,1 558, 271, ,48 2,63,968 1,141, , 369,8 2,965 11, ,723 (56,77) ,4 224,1 118,278 72,59 29,554 (556,946) ,4 24,6 129,64 82,54 1,17, , , 354,3 HSSNG MSSNG 1,463,83 672, HSSNG HSSNG HSSNG HSSNG ANNUAL AVERAGE ,81 354, ,666 37,73 ANNUAL AVERAGE 21,471 COMAL SPRNGS ANNUAL AVERAGE SAN MARCOS SPRNGS 119,

40 L TABLE 8.2 NUMBER OF WELLS N THE EDWARDS AQUFER, SAN ANTONO REGON, FOR WHCH RECORDS WERE OBTANED FROM TEXAS WATER COMMSSON CENTRAL RECORDS FLE (11/91) COUNTY Bexa Comal TYPE OF RECORD Located Plotted Unplotted Total Located Plotted Unplotted (SOURCE: STEN, 1993) DOMESTC PUBLC SUPPLY AND NDUSTRAL RRGATON TOTAL , Total 1, ,88 Hays Located Plotted Unplotted Total Medina Uvalde Located Plotted Unplotted Total Located Plotted Unplotted Total [ TOTAL 3, ,

41 . EXPl.ANA lion ---- Bocn:Say of Edwanfs kfi,fo Reehaoe Aea,.. - Lowe Bounday of Edwads APJ,e Rechage Aea... M.. Westen and Eastem Limits of Edwads Aquife /-Location of Bad Wate Line Location of Majo Wei (Public Supply, ndustia o liga.tion).f :-.,. ClO,.....,..;.... ', ',,. '--....,co i..,...co.::: t;-< - -- NUMBER AND USE OF MAJOR WEU.S , 15 ll: J so ' L Figue Medina Locations of Majo Wells -37 Bexa County

42 domestic/livestock wells located ove the Edwads Aquife. stein (1993) found that the most dense concentation of wells ae located in the vicinity of Comal and San Macos Spings. The wells in the vicinity of the spings ae mostly domestic wells. The poximity of the lage numbe of domestic wells to the spings ceates an instantaneous effect on the local atesian head, and theefoe, these domestic wells have an immediate impact on diminished spingflow (Stein 1993). stein estimated that thee ae between 1, to 2, wells that withdaw wate fom the Edwads Aquife, which supplies wate to ove 1.3 million people in the San Antonio Region. Of these wells, Stein estimates that about s,ooo ae actually ecoded in the TWDB files. n examining shot tem measues that might be taken to influence spingflow, the impact of use fom the lage numbe of domestic wells in the immediate vicinity of the spings should not be ignoed. Pumping fom these wells has a moe diect and immediate effect on the spings, than almost any othe wells in the aquife. The annual histoical sping dischage fo majo spings 18 vaied fom 69,8 af in 1956 to 58,3 af in 1977, with an aveage annual sping dischage fo the peiod 1934 though 1991 of 354,126 af. Of this annual aveage Comal Spings aveaged appoximately 21,47 af/y o appoximately 6 pecent. Accoding to EUWD ecods, Comal and San Macos Spings aveage appoximately 86 pecent of the total sping dischage fom the Edwads Aquife on an annual basis (EUWD 1989). A flow-duation cuve fo Comal Spings is shown in Figue 8. 2 (USGS 1995). This cuve indicates that Comal Spings, duing the peiod 193 though 1994, had a dischage ate of less than 15 cubic feet pe second (cfs) appoximately 1 pecent of the time, 18 Majo spings include san Macos spings in Hays County, Comal and Hueco spings in comal County, san Antonio and San Pedo Spings in Bexa County, and Leona Rive Spings in Uvalde County (EUWD 1991). -38

43 m L a ii"' -6 1:e... --!!ee t. t. t. i Figue i t t :. t 1 t K :. --t t. t t 1... ;!. t t "" fi8 :! a Flow Duation cuve Fo -39. :. a: :... t 1 s:... t!!.. :.... i 1.! t... t : t -y. : e tf f! a l t t. tl! 8 t.... t ;. t e _,!ii: - 1. i. i J! ; 2:...!! _,,....! i t : O:f t!.. il: t t.. t t )( f t f!- : t. f...! :. i 2!ii :: -. t!:! ;::... t 2: e! ;.. = t t t t K!! t. : t... ; : B t... a t...: t : N t. 1 :.: t ; t t t -.. i :! 1 t t "'.,;. t! ;::.!..,;... u - - _..,.,;.,; Comal Spings.

44 and a dischage ate of less than 6 cfs appoximately 2.2 pecent of the time. Flow-duation cuve analyses fo Comal Spings daily dischage fo each individual calenda month with espect to the REWRP is shown below: MONTH JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC DALY DSCHARGE OR EQUAL TO LESS THAN DALY DSCHARGE LESS THAN 15 CFS OR EQUAL TO 6 CFS

45 l. SECTONll EDWARDS AQUF'ER- AN UNDERGROUND RVER? Wells A. Hutchins (The Texas Law on Wate Rights) states: "A definite undegound steam has the same chaacteistics as those of a watecouse on the suface. Even though buied in the gound, it has been teated histoically on the same pinciples as suface steams, both unde the law of appopiation and at common law. As ecently as 1931, the Aizona Supeme Cout held that to establish judicially the existence of an alleged subteanean steam, thee must be affoded "clea and convincing poof to the satisfaction of a easonable man, not only that thee ae subteanean wates, but that such wates have a definite bed, banks, cuent with the odinay meaning of the tems as above set foth, and the evidence must establish with easonable cetainty the location of such bed and banks." Using this standad, as well as, my expeience as a hydologist, it is my opinion that a suface wate couse possesses the following chaacteistics, none of which ae satisfied by the Edwads Aquife: A PLOW WTHN A DEFNED WATER COURSE, WTH READLY DEFNABLE BEDS AND BANKS A ive has a definable and eadily identifiable bed and banks. The Edwads Aquife has genealized flow paths, but flow channels within the Aquife cannot be defined, located o identified with specific bed and banks. No ae thee land suface indications which allow one to discen the path of an undegound ive. DSCERNABLE PLOW A ive has obsevable wate flow, i.e. movement at a discenible velocity in a paticula diection. The Edwads -1

46 . Aquife, as a whole, is without obsevable flow velocity and has flow paths conveying wate in many diections. FREE WATER SURFACE AND UNDERFLOW A suface wate ive has a fee wate suface, that is a suface that is in contact with the atmosphee. A suface wate ive can have undeflow in the sediments and deposits that make up its bed and banks. But such undeflow is in continual contact with the suface ive. Wate in the Edwads Aquife, howeve, is not undeflow. t sepaates fom its suface wate souce and moves independently in a diffeent diection, by a diffeent oute, at a diffeent speed, and to a diffeent destination. Although the Edwads Aquife does has a fee wate suface within its wate table zone, most of its wate is stoed unde atisan (pessue), without a fee wate suface. FLOW THAT ZS SUBJECT TO OPEN CHANNEL COHDXTZONS A ive is subject to the physics and hydaulics of open channel flow. The Edwads Aquife is not, and is subject to flow in confined and unconfined poous media. The geogaphical limits of the Edwads Aquife can be defined with easonable cetainty, but the Aquife as a whole unit is not an undegound ive. The Edwads is an undegound fesh and saline wate stoage unit, whose stoage chaacteistics and flow conveyance systems ae subject to the physics and dynamics of flow in and though poous media. n othe wods, the Edwads is an undegound fomation and aquife, and does not possess the hydaulic chaacteistics of a suface wate ive. f analogous to any suface wate unit, the Edwads Aquife is analogous to a wateshed o ive basin, as ae othe gound wate aquifes. The Aquife has geogaphic limits, as does a ive basin. The Aquife has collection channels and flow outes, as -2

47 does a ive basin. The Aquife has natual dischage points, as does a ive basin. The Aquife is a geogaphic wate collection unit, as is a ive basin. Howeve, the analogy beaks down. Within a ive basin thee ae clealy identifiable tibutaies, ceeks and ives that collect wate oiginating fom ainfall and channels it to a common dischage point. Within a ive basin collection paths ae clealy identifiable and can be pecisely located and quantified. While the Edwads Aquife collects wate via echage, which also oiginates fom ainfall, its channels ae specifically un-identifiable flow paths to undegound stoage aeas and to numeous dischage points. Within the Edwads Aquife, thee ae flow outes analogous to the tibutaies and ives chaacteistic of watesheds, but with at least fou majo exceptions: (1) the Edwads flow outes cannot be clealy identified and located; (2) flow outes ae small o minute, compaed to flow paths of a ive basin; (3) do not demonstate the consistent consolidation o down-gadient convegence that is chaacteistics of suface watecouses; and ( 4) the Edwads Aquife, as a whole, does not exhibit a discenable velocity. The Edwads Aquife is like all othe majo and mino aquife systems. Any aquife's boundaies, genealized diection of flow and ate, echage souces, dischage points, and geneal composition can be identified and geneally quantified. Possibly the only thing that sets the Edwads Aquife apat fom othe aquifes is that it has a highe tansmissivity. But, having a highe tansmissivity, does not make the Edwads Aquife an undegound ive. Plaintiffs in this case, as well as, othe individuals have suggested that the Edwads Aquife is an undegound ive. t is my pofessional opinion, that the Edwads Aquife is not an undegound ive due to the above easons. -3

48 i l l l l f f t t t t ' l SECTONm EDWARDS AQUF'ER- WATER QUALTY SSUES SSUE NO. 1: OVERPUMPNG OF 'l'be AQUFER WJ:LL NO'l' CAUSE REGONAL WA'l'BR QUALTY PROBLEMS The feshwate potion of the Edwads Aquife may expeience wate quality poblems fom the following thee souces: 1. Movement of the "bad-wate" line; 2. Communication fom the Glen Rose Aquife; and 3. Deteioation of suface wate quality ove in the echage zone. As discussed in Section, within the fesh wate potion of the Edwads Aquife, thee is vey little oppotunity fo the movement of the "bad-wate" line and limited communication fom the Glen Rose Aquife. Given these two facts, it is my pofessional opinion that, except on a vey localized basis, Aquife wate quality deteioation will not occu due to ovepumping. A significantly geate immediate and genuine theat to the Aquife's wate quality is attibutable to development and ubanization ove and upsteam of the Aquife's echage zone. SSUE NO. 2: A COMAL SPRNGFLOW RATE OF LESS '!'BAN 2 CFS S UNRELATED TO WATER QUALTY N THE AQUFER Histoical expeience clealy demonstates that neithe the "badwate" line o communication with the Glen Rose aquife caused egional wate quality poblems duing the sevee 195's dought, when Comal Spings went dy. Theefoe, eduction of spingflow below an abitay steamflow dischage ate of eithe 2 o 15 cfs at Comal Spings is anticipated to have no elation to Aquife wate quality and should not esult in wate quality poblems to the Edwads Aquife. -1

49 ', E '... DSCUSSON A. Movement of the ":bad-wate" line As descibed in Section of this epot, the southen bounday of the confined potion of the Edwads Aquife is the "bad-wate" line. This line is set whee the concentation of 1, ooo mg/1 (milligams pe lite) of dissolved solids occus in the Aquife. The concentations of dissolved solids at given sampling points vay slightly with time, but the lateal position of the "badwate" line has not significantly shifted ove time (TWDB 1986). n addition, thee is no indication that the "bad-wate" line shifted significantly, even duing the 195's dought when Comal Spings went dy. The diffeence with wate quality between the bad wate zone and the fesh wate zone of the Edwads Aquife occus because thee is little o no ciculation of wate in the bad wate zone. Wate has esided in the bad wate zone fo such a length of time that mineals have dissolved fom the ocks in lage enough quantities to poduce high levels of dissolved solids. Given the extemely slow movement of wate within the bad wate zone, eduction in head of the in the fesh wate zone, if it has any effect at all, should esult in only mino and localized inflow of saline wate. n geneal, the aquife in the saline-wate zone (i.e. bad wate zone) has consideable less capacity to tansmit wate than the aquife in the feshwate zone because an integated netwok of cavenous zones has not be developed by ciculation of feshwate As a compaison, the tansmissivity of the saline wate zone (668 ft 2 /d) is 2 times less than the tansmissivity of the feshwate zone {134, ft 2 /d) fo the feshwate zone (USGS 1986). n addition, faults significantly disupt the lateal continuity of the geologic fomations at places in Bexa County, impeding o peventing flow in faulted aeas. These factos seve to estict -2

50 ., ' [ '. lateal gound wate flow acoss the "bad-wate" line. This is futhe confimed by an examination of Aquife coss-sections which tansect the confined and "bad-wate" zones. Appoximately 3 such coss-sections wee pepaed by T. A. Small (USGS 1986). The USGS (1986) found that some undetemined amount (but elatively small due to low hydaulic gadients and low saline-wate zone tansmissivities) flow pobably moves fom the feshwate to the saline wate pat of the aquife in Kinney, Uvalde and westen Medina Counties and fom the saline-wate to feshwate pat of the aquife in Hays and Tavis Counties. t should be noted that fo puposes of mathematical modeling, the TWDB teats the "bad-wate" line as an impemeable aquife bounday, with the exception of a small aea in southeast Uvalde County. Based on a eview of the liteatue and vaious mathematical modeling studies, egional Edwads Aquife wate quality degadation will not occu as a esult of updip movement of the "bad-wate" line. This line has limited oppotunity fo updip movement, and if it does move up-dip due to exteme conditions in the fesh wate zone, its movement will be vey limited, not causing a teat to egional wate quality. B. Communication fom the Glen Rose Aquife The Edwads Aquife also has some limited hydologic communication with the undelying and 11 pooe" wate quality Glen Rose Aquife (EUWD 1995). Because of faulting, the Edwads Aquife in many aeas ove the 18-mile length between the two gound-wate divides is juxtaposed to the Glen Rose Aquife. Both at the suface and a depth, and theefoe, the Glen Rose may dischage diectly into the Edwads Aquife. Regionally, undeflow fom the Glen Rose Fomation to the Edwads Aquife along the Balcones fault zone can occu by gound wate moving lateally in a down-gadient diection within the Glen Rose and enteing the Edwads aquife though fault planes. The amount of gound wate in tansit is dependent on the -3

51 l <.._ length of the line of enty (fault plane) though which wate entes the Edwads Aquife, the wate level gadient acoss the fault plane fom the Glen Rose to the Edwads Aquife, and the effective tansmissivity fo the Glen Rose Aquife upgadent and along this line. The EUWD (1995) estimates that the appoximate ange of total Glen Rose undeflow to the Edwads Aquife would be about 2,7 to about 11,4 af/y in the San Antonio Region. As compaed to the total Edwads Aquife wate balance, these estimates indicate that the Glen Rose contibutes less than 2 pecent of the total wate budget duing aveage echage conditions. The EUWD (1995) also estimated that, based on geochemical models, the chemical content of wate epesentative of the Edwads Aquife in the San Antonio Region include a small amount, less than 1 pecent Glen Rose wate (EUWD 1995). Thus, local communication between the fomations occus, but without significant impact on oveall wate quality of the Edwads Aquife, due to the low tansmissivity of the Glen Rose. -4

52 SECTON V. Effects of Selected Pumpage on Spingflow 1. Effects of Client Pumpage DGRA, nc., epesents 3 fames 1 in uvalde County who iigate cops fom Edwads Aquife wells. n 1995, these fames have a total of twelve wells, which iigate appoximately 2,46 aces of land located, within an appoximate 1-mile adius of Knippa, Texas. igated cops include con, cotton, sesame, milo, and sunflowe. DGRA, nc. simulated the effect on Comal Spings and San Macos Spings flow assuming the fames had to totally cutail thei pumpage fo the peiod May 2, 1995, though Decembe 31, To achieve this simulation, DGRA, nc. used the cuent vesion of the TWDB's Edwads Aquife model (GW-SM V). The following fou model simulations wee made: Simulation No. 1 - Base Run fo the Peiod Januay 1978 though Decembe 1989, Using 1983 Pumpage Levels, Histoical Rechage and 1978 Stating Heads Simulation No. 2 - simulation No. 3 - Fames Cutailment Run (i.e. cutailment of iigation wate fo the May 15 though Decembe 31 peiod) Applied in the Yea 1984 to Simulate a Low Rechage Yea Fames cutailment Run (i.e. cutailment of iigation wate fo the May 15 though Decembe 31 peiod) Applied in the Yea 1978 to Simulate an Aveage Rechage Yea M. Danny McFadin, Knippa, Texas; M. Tommy Walke, Uvalde, Texas; and M. Cal Muecke, Knippa, Texas. V-1

53 Simulation No. 4 - Fames cutailment Run (i.e. cutailment of iigation wate fo the May 15 though Decembe 31 peiod) Applied in the Yea 1985 to Simulate a High Rechage Yea Simulation Nos. 2, 3 and 4 wee compaed to Simulation No. 1 (Base Run) to detemine the impact of total iigation cutailment fo the fames fo the peiod May 2, 1995 though Decembe 31, 1995, such cutailments occued in a low, aveage and high echage yea. The fames epoted iigation use fo the peiod Januay 1, 1995 though May 19, 1995, wee used in Simulation Runs Nos 2, 3, and 4. The esults of the effects of the fame's total cutailment of pumpage fo the peiod May 2, 1995, though Decembe 31, 1995 ae shown below: YEAR MONTH FOR LOW RECHARGE YEAR 1978 DFFERENCE S SPRNG FLOW (ACRE-FEET) CO MAL SPRNGS SAN MARCOS SPRNGS TOTAL V-2

54 l YEAR KON'l'B TOTAL YEAR MON'l'B TOTAL FOR AVERAGE RECHARGE YEAR 1978 DXFFBRENCE S SPRNG FLOW (ACRE-FEET) CO MAL SPRNGS SAN MARCOS SPRNGS FOR BGB RECHARGE YEAR 1985 DFFERENCE S SPRNG FLOW (ACRE-FEET) COXAL SPRNGS SAN MARCOS SPRNGS l.Q_J_ 59.9 As shown above, total cutailment of fame's pumpaqe fo the peiod May 2, 1995, though Decembe 31, 1995, as applied to the V

55 low (1984), aveage (1978) and high echage (1985) yeas only esulted in a total Comal Spings flow eductions of 88.4 af, 66.6 af and 59.9 af, espectively. Similaly, San Macos Spings exhibited eductions fo the low (1984), aveage (1978) and high echage (1985) yeas of.4 af,.2 af, and.4 af, espectively. Taking the maximum Comal Spings flow eduction of 88.4 af fo the low echage yea of 1984, only esults in an aveage decease in spingflow dischage ate of o. 2 cfs. This steamflow eduction is negligible and well within modeling eo, and as such the fames' cutailment can be consideed as having no impact on Comal Spings flow. Likewise, the fame's pumpage cutailment will have no impact on San Macos Spings flow. conclude fom this analysis that cutailment of the thee fames' iigation usage fo the emainde of 1995 would have no impact of Comal Spings and San Macos Spings flows whethe 1995 is a low, an aveage, o a high echage yea. 2. Effects of Agicultual and Municipal Pumpage t_ n ode to detemine the elative effects of agicultual and municipal pumpage on Comal Spings and San Macos Spings dischage, DGRA, nc. pefomed the following analyses, using the cuent vesion of the TWDB's Edwads Aquife model (GW-SM V): Simulation No. 1 - Simulation No. 2 - Base Run fo the Peiod Januay 1978 though Decembe 1989, Using Histoical Pumpage Levels, Histoical Rechage and 1978 Stating Heads Reduce Agicultual Pumpage in All Counties Withdawing Wate Fom the Edwads Aquife by V-4

56 the factos of 1%, 25% and 5%, beginning the Yea 1983 fo the Simulation Peiod Januay 1978 though Decembe 1989, While Maintaining Othe Pumpage Uses at Histoical Levels Simulation No. 3 - Reduce Municipal Pumpage in All Counties Withdawing Wate Fom the Edwads Aquife by the Same Amount (volumetic quantity not pecentage) as Repesented by 1%, 25% and 5% Agicultual Reductions, Beginning in the Yea 1983 fo the Simulation Peiod Januay 1978 though Decembe 1989, While Maintaining Othe Pumpage Uses at Histoical Levels Simulation No. 4 - Reduce Municipal Pumpage in All Counties Withdawing Wate Fom the Edwads Aquife by the factos of 1%, 25% and SO%, beginning the Yea 1983 fo the Simulation Peiod Januay 1978 though Decembe 1989, While Maintaining Othe Pumpage Uses at Histoical Levels The esults of these simulations ae shown below: ACTJ:ON 1% AGRCULTURAL REDUCTON 25% AGRCULTURAL REDUCTON 5% AGRCULTURAL REDUCTON REDUCTON N COMAL SPRNGS FLOW (AF) TOTAL FLOW AVG. FLOW 29, , ,972 1,666 V REDUCTJ:ON J:N SAN MARCOS FLOW (AF) SPRNGS TOTAL FLOW AVG. FLOW 1, , ,137 73

57 . MUNCPAL REDUCTON EQUAL TO 1% AGRCULTURAL CUT MUNCPAL REDUCTON EQUAL TO 2S% AGRCULTURAL CUT MUNCPAL REDUCTON EQUAL TO SO% AGRCULTURAL CUT 1% MUNCPAL REDUCTON 2S% MUNCPAL REDUCTON SO% MUNCPAL REDUCTON 7,8S , ,13 2,6 16, S,77 3,989 33, ,1S 1,3S8 11, ,471 3,2S6 27, S19,44 6,179 S3, Examination of the above data damatically shows that fo coesponding eductions (i.e. 1%, 2S% and SO%) in agicultual vesus municipal pumpage that agicultual pumpage that municipal pumpage has an aveage of 3.7 times geate effect on Comal Spings flow and 8.S times geate effect on San Macos Spings flows than does agicultual pumpage. When compaing equal volumetic eductions between agicultual and municipal pumpage, municipal pumpage has an aveage 2.4 times geate effect on Comal Spings flow and an aveage S.3 times geate effect on san Macos Spings flow. The geate impact of municipal pumpage ove agicultual pumpage is lagely due to the fact that most agicultual pumpage occus in Uvalde County and most municipal pumpage occus in Bexa County, i.e. agicultual pumpage is centeed futhe fom the spings than municipal. Also, this may exhibit that Uvalde Pool aea of the Edwads Aquife may not diectly feed flow to Comal and San Macos Spings, as does the Edwads' pool that supplies municipal wate to Bexa County. V-6

58 conclude fom these analyses that the REWRP may be biased against agicultual uses, since thei wate usage has a much lesse impact on Comal Spings and San Macos Spings flow than does pumpage by municipal uses. V-7

59 V. REVSED EMERGENCY REDUCTON PLAN WTHDRAWAL The Revised Emegency Withdawal Reduction Plan {REWRP), Mach 331, 1995, has the following majo deficiencies: REWRP PROPOSES PUKPAGE LMTATONS ON MAJOR USERS WTHOUT REGARDS TO WELL LOCATONS The plan needlessly esticts pumping fom wells too distant to have a impact upon Comal Spings and San Macos Spings flow duing the yea in which the emegency eduction is equied. While such estictions may seve a pupose in a long-tem aquife management plan, they ae pointless and punitve as a shot-tem, emegency management measue. RBWRP NEGLECTS REGULATON OP THE HUNDREDS AND POSSBLY THOUSANDS OP DOMESTC AND LVESTOCK WELLS LOCATED NEAR THE SPRNGS Domestic and livestock wells located nea the spings have a diect and immediate effect on spingflows. Fo a shot-tem REWRP to be effective, wells in the immediate vicinity of the spings cannot be ignoed REWRP DOES NOT FUNCTON ON AN EMERGENCY BASS AS NTENDED The REWRP's ationale and intended pupose is as a shot-tem, emegency measue to peseve spingflow. By its own tems howeve, it would implement 11 emegency 11 contols on iigation almost 8% of the time. A plan implemented with this fequency should focus upon and utilize long-tem management stategies. V-1

60 ' l THE REWRP S BASED AND UNFAR TO RRGATON WATER USERS The REWRP ignoes the fact that iigation pumpage effects on Comal Sping flows 2 to 3 times less than municipal pumpage on a shot-tem emegency basis. An analysis pesented in Section V and an independent Texas A&M Univesity study clealy demonstates that duing the same yea iigation pumpage deceases Comal Sping by a facto of 2. 4 to 3. o times less than equivalent amount of municipal pumpage and about 5 times less fo San Macos Spings. RBWRP PROVDES FOR UNFAR COMPENSATON The REWRP povides fo financial compensation to public wate puveyos, via doubling of wate ates, fo enfocing discetionay wate use, but does not povide compensation to iigation and industial wate uses that ae equied to educe non-discetionay uses. RBWRP REQUREMENT OF SURCHARGNG BY MUNCPAL WATER PURVEYORS TO TS CUSTOMERS FOR DSCRETONARY WATER USE MAY BE N VOLATONS OF PURVEYOR'S WATER TARFFS The REWRP equiement fo suchaging customes of public wate puveyos may be in violation of wate taiffs. Amendments to puveyo's wate taiffs to allow fo such suchaging cannot be made by within the 1995 peiod of the REWRP. PLAN GNORES ECONOMCS MPACT The REWRP ignoes the possible temendous economic impact to agicultual, municipal and industial wate uses. PLAN S RESTRCTED TO USERS OF CONFNED USERS The REWRP appaently equies limitations on wate uses who withdaw wate fom only the confined (i.e. atesian) potion of the Edwads Aquife, as infeed in the REWRP definition of the wod 11 Aquife". V-2

61 . PLAN PROHBTS WTHDRAWALS OF WATER FROM THE AQUFER J!'OR WELLS DRLLED AFTER JUNE 1, 1993 The pohibition on withdawal fom wells dilled afte June 1, 1993 is uneasonable and disciminatoy. Many Edwads Aquife wate uses have dilled wells afte June 1, 1993, fo additional supply to meet expanding demands andjo fo eplacement wells. mposing this equiement will be extemely budensome and pejudicial. V-3

62 BmLOGRAPHY LTERATURE REVEWED BY DONALD RAUSCHUBER Alexande 1 Kenneth Bowe 1 CORRELATON OF STRUCTURAL LNEAMENTS AND FRACTURE TRACES TO WATER-WELL YELDS N THE EDWARDS AQUFER, CENTRAL TEXAS (Thesis), Decembe 199 Dapples, E.C., BASC GEOLOGY FOR SCENCE AND ENGNEERNG, 1959 Edwads Aquife Reseach and Data Cente - Southwest Texas state Univesity 1 HYDROCHEMCAL NVESTGATON OF THE COMAL AND HUECO SPRNG SYSTEMS, COMAL COUNTY, TX, August 1987 Edwads Aquife Reseach and Data Cente - Southwest Texas state Univesity, HYDROLOGC AND HYDROCHEMCAL DATA FOR THE EDWARDS AQUFER N HAYS AND COMAL COUNTES, OCTOBER 1981 TO SEPTEMBER 1983, July 1985 Edwads Aquife Reseach and Data Cente - Southwest Texas state Univesity, HYDROLOGC AND HYDROCHEMCAL DATA FOR THE EDWARDS AQUFER N HAYS AND COMAL COUNTES 1 OCTOBER 1983 TO JUNE Decembe 1985 Edwads Aquife Reseach and Data Cente - Southwest Texas state Univesity 1 PROCEEDNGS - PERSPECTVES ON THE EDWARDS AQUFER (BALCONES FAULT ZONE), Apil 3, 1982 Edwads Aquife Reseach and Data Cente - southwest Texas State Univesity, REGRESSON ANALYSS OF THE SAN MARCOS SPRNG FLOWS AND WATER LEVELS OF THE NDEX WELL N SAN ANTONO, Febuay 1988 Edwads Aquife Reseach and Data Cente - Southwest Texas State Univesity, STOCHASTC DROUGHT ANALYSS OF THE EDWARDS AQUFER, August 199 Edwads Undegound Wate Distict, 1994 REVEW AND UPDATE OF THE POSTON OF THE EDWARDS AQUFER FRESHWATER/SALNE-WATER NTERFACE FROM UVALDE TO KYLE, TEXAS, Repot 94-5, Novembe 1994 Edwads Undegound Wate Distict, CHEMCAL ANALYSES OF WATER FROM OBSERVATON WELLS N THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1963, Bulletin 4, Januay 1964 Edwads Undegound Wate Distict, CHEMCAL ANALYSES OF WATER FROM OBSERVATON WELLS N THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1964, Bulletin 7, Mach 1965 Edwads Undegound Wate Distict, COMPLATON OF HYDROLOGC DATA FOR THE EDWARDS AQUFER, SAN ANTONO AREA, TEXAS, 1985, WTH SUMMARY, Bulletin 45, July 1987 B-1

63 t Edwads Undegound Wate Distict, COMPLATON OF HYDROLOGC DATA FOR THE EDWARDS AQUFER, SAN ANTONO AREA, TEXAS, 1986, WTH SUMMARY, Bulletin 46, Febuay 1988 Edwads Undegound Wate Distict, COMPLATON OF HYDROLOGC DATA FOR THE EDWARDS AQUFER, SAN ANTONO AREA, TEXAS, 1987, WTH SUMMARY, Bulletin 47, Septembe 1988 Edwads Undegound Wate Distict, COMPLATON OF HYDROLOGC DATA FOR THE EDWARDS AQUFER, SAN ANTONO AREA, TEXAS, 1988, WTH SUMMARY, Bulletin 48, Novembe 1989 Edwads Undegound Wate Distict, COMPLATON OF HYDROLOGC DATA FOR THE EDWARDS AQUFER, SAN ANTONO AREA, TEXAS, 1989, WTH SUMMARY, Bulletin 49, Decembe 199 Edwads Undegound Wate Distict, EDWARDS AQUFER GROUND-WATER DVDES ASSESSMENT SAN ANTONO REGON, TEXAS, Repot 95-1, Decembe 1994 Edwads Undegound Wate Distict, EDWARDS AQUFER HYDROGEOLOGC REPORT FOR 1993, Repot 94-4, Decembe 1994 Edwads Undegound Wate Distict, EDWARDS/GLEN ROSE HYDROLOGC COMMUNCATON, SAN ANTONO REGON, TEXAS, Repot 95-3, Mach 1995 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, , SAN ANTONO AREA, TEXAS, Bulletin 2, July 1963 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1965, Bulletin 11, July 1966 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1966, Bulletin 14, July 1967 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1967, Bulletin 17, July 1968 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1969, Bulletin 23, August 197 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 197, Bulletin 26, May 1971 B-2

64 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1971, Bulletin 29, June 1972 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1972, Bulletin 31, July 1973 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1973, Bulletin 32, July 1974 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1974, Bulletin 34, July 1975 Edwads Undegound Wate Distict, GROUND-WATER DSCHARGE FROM THE EDWARDS AND ASSOCATED LMESTONES, SAN ANTONO AREA, TEXAS, 1975, Bulletin 35, July 1976 Edwads Undegound Wate Distict, HYDROLOGC NVESTGATONS OF THE EDWARDS AND ASSOCATED LMESTONES N THE SAN ANTONO AREA, TEXAS, PROGRESS REPORT, , Mach 1972 Edwads Undegound Wate Distict 1 RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES, , SAN ANTONO AREA, TEXAS, Bulletin 3, Octobe 1963 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO, TEXAS, 1963, Bulletin 6, Octobe 1964 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO, TEXAS, 1965, Bulletin 12, Octobe 1966 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO, TEXAS, 1966, Bulletin 15, August 1967 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO, TEXAS, 1967, Bulletin 18, August 1968 B-3

65 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, AQUFER HEAD, AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO, TEXAS, 1968, Bulletin 21, June 1969 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON 1 WATER LEVELS AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO AREA, TEXAS, 1969, Bulletin 24, June 197 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON, WATER LEVELS AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO AREA, TEXAS, 197, Bulletin 27, Apil 1971 Edwads Undegound Wate Distict, RECORDS OF PRECPTATON 1 WATER LEVELS AND GROUND-WATER RECHARGE TO THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO AREA, TEXAS, 1971, Bulletin 3, May 1972 Edwads Undegound Wate Distict, REGONAL DSTRBUTON OF PERMEABLTY N THE EDWARDS AQUFER, Repot 95-2, Januay 1995 Edwads Undegound Wate Distict, REGONAL DSTRBUTON OF PERMEABLTY N THE EDWARDS AQUFER, Repot 95-2, Map Pocket Plates 1-6 Edwads Undegound Wate Distict, REGONAL SPECFC YELD OF THE EDWARDS AND ASSOCATED LMESTONES N THE SAN ANTONO, TEXAS AREA, August 1973 Edwads Undegound Wate Distict, REGONAL WATER RESOURCES PLAN, July 1988 Edwads Undegound Wate Distict and u.s. Amy Enginee Distict, SURVEY REPORT ON EDWARDS UNDERGROUND RESERVOR, Vol. 3 1 Januay Fette, C.W., APPLED HYDROGEOLOGY, Thid Edition, Thid Edition, 1994 Feese, Nichols and Endess fo Texas Wate Development Boad, REPORT ON SURFACE WATER SOURCES FOR SUPPLEMENTNG THE EDWARDS UNDERGROUND RESERVOR, Januay 1966 Guadalupe-Blanco Rive Authoity and HDR Engineeing, REGONAL WATER PLAN FOR THE GUADALUPE RVER BASN, Januay 1991 Guadalupe-Blanco Rive Authoity, THE EDWARDS AQUFER UNDERGROUND RVER OF TEXAS, Apil 1988 Keplinge, K.O. and McCal, B.A. 1 THE EFFECTS OF RECHARGE, AGRCULTURAL PUMPNG AND MUNCPAL PUMPNG ON SPRNGFLOW AND PUMPNG LFTS WTHN THE EDWARDS AQUFER: A COMPARATVE ANALYSS USNG THREE APPROACHES, Apil 13, 1995 B-4

66 Mooe, Joe G. 1 REVSED EMERGENCY WTHDRAWAL REDUCTON PLAN FOR THE EDWARDS AQUFER, August 1, 1994 San Antonio, City of and Glass Envionmental Consultants, nc., fo Texas Depatment of Wate Resouces, REPORT ON SUTABLTY OF AVALABLE WATER QUALTY DATA FOR DETERMNNG THE MPACTS OF NONPONT SOURCES ON SAN ANTONO 1 TEXAS AND SURROUNDNG AREAS, Januay 1982 Special Committee on the Edwad Aquife, COMMTTEE REPORT TO THE 72ND LEGSLATURE, Januay 8, 1991 Southwest Texas State Univesity, PROCEEDNGS - SAN MARCOS & COMAL SPRNGS SYMPOSUM, Decembe 2-3, 1988 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF BEXAR COUNTY, TEXAS, May 1947 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF THE SAN ANTONO AREA 1 TEXAS - A PROGRESS REPORT OF CURRENT STUDES 1 Bulletin 5412, August 1954 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF THE SAN ANTONO AREA, TEXAS - A PROGRESS REPORT ON CURRENT STUDES, Bulletin 568, Vol., July 1956 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF THE SAN ANTONO AREA, TEXAS - RECORDS OF WELLS AND SPRNGS, Bulletin 568, Vol., Pat, July 1956 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF THE SAN ANTONO AREA, TEXAS - RECORDS OF DRLLERS' LOGS, Bulletin 568, Vol., Pat, July 1956 Texas Boad of Wate Enginees, GROUND-WATER RESOURCES OF THE SAN ANTONO AREA, TEXAS - WATER LEVELS N WELLS, CHEMCAL ANALYSES OF WATER, RECORDS OF STREAM FLOW AND RESERVOR CONTENTS, DSCHARGE MEASUREMENTS, AND PRECPTATON N THE SAN ANTONO AREA, TEXAS, Bulletin 568, Vol., Pat, July 1956 Texas Boad of Wate Enginees, RECHARGE, DSCHARGE, AND CHANGES N GROUND-WATER STORAGE N THE EDWARDS AND ASSOCATED LMESTONES SAN ANTONO AREA, TEXAS 1 A PROGRESS REPORT ON STUDES , Bulletin 621, Januay 1962 Texas Boad of Wate Enginees, RECORDS OF WATER-LEVEL MEASUREMENTS N KNNEY, UVALDE AND VAL VERDE COUNTES, TEXAS, 1929 to MARCH 1956, Bulletin 5611, May 1956 Texas Depatment of Wate Resouces, GROUND-WATER RESOURCES AND MODEL APPLCATONS FOR THE EDWARDS (BALCONES FAULT ZONE) AQUFER N THE SAN ANTONO REGON, Repot 239, Octobe 1979 B-5