Appendix G: Supplemental Water Supply Information

Transcription

1 California Water Service 2015 Urban Water Management Plan Visalia District Appendix G: Supplemental Water Supply Information DWR Groundwater Bulletin 118 TID-City of Visalia Water Exchange Agreement City of Visalia Groundwater Impact Fee Memo

2 California Water Service 2015 Urban Water Management Plan Visalia District Appendix G: Supplemental Water Supply Information DWR Groundwater Bulletin 118

3 Chapter 7 S an Joaquin River Hydrologic Region Tulare Lake Hydrologic Region CALIFORNIA S GROUNDWATER UPDATE

4 Chapter 7 Tulare Lake Hydrologic Region Figure 37 Tulare Lake Hydrologic Region 176 DWR - BULLETIN 118

5 Chapter 7 Tulare Lake Hydrologic Region Basins and Subbasins of Tulare Lake Hydrologic Region Basin/subbasin Basin name 5-22 San Joaquin Valley Kings Westside Pleasant Valley Kaweah Tulare Lake Tule Kern County 5-23 Panoche Valley 5-25 Kern River Valley 5-26 Walker Basin Creek Valley 5-27 Cummings Valley 5-28 Tehachapi Valley West 5-29 Castaic Lake Valley 5-71 Vallecitos Creek Valley 5-80 Brite Valley 5-82 Cuddy Canyon Valley 5-83 Cuddy Ranch Area 5-84 Cuddy Valley 5-85 Mil Potrero Area Description of the Region The Tulare Lake HR covers approximately 10.9 million acres (17,000 square miles) and includes all of Kings and Tulare counties and most of Fresno and Kern counties (Figure 37). The region corresponds to approximately the southern one-third of RWQCB 5. Significant geographic features include the southern half of the San Joaquin Valley, the Temblor Range to the west, the Tehachapi Mountains to the south, and the southern Sierra Nevada to the east. The region is home to more than 1.7 million people as of 1995 (DWR, 1998). Major population centers include Fresno, Bakersfield, and Visalia. The cities of Fresno and Visalia are entirely dependent on groundwater for their supply, with Fresno being the second largest city in the United States reliant solely on groundwater. Groundwater Development The region has 12 distinct groundwater basins and 7 subbasins of the San Joaquin Valley Groundwater Basin, which crosses north into the San Joaquin River HR. These basins underlie approximately 5.33 million acres (8,330 square miles) or 49 percent of the entire HR area. Groundwater has historically been important to both urban and agricultural uses, accounting for 41 percent of the region s total annual supply and 35 percent of all groundwater use in the State. Groundwater use in the region represents about 10 percent of the State s overall supply for agricultural and urban uses (DWR 1998). The aquifers are generally quite thick in the San Joaquin Valley subbasins with groundwater wells commonly exceeding 1,000 feet in depth. The maximum thickness of freshwater-bearing deposits (4,400 feet) occurs at the southern end of the San Joaquin Valley. Typical well yields in the San Joaquin Valley range from 300 gpm to 2,000 gpm with yields of 4,000 gpm possible. The smaller basins in the mountains surrounding the San Joaquin Valley have thinner aquifers and generally lower well yields averaging less than 500 gpm. CALIFORNIA S GROUNDWATER UPDATE

6 Chapter 7 Tulare Lake Hydrologic Region The cities of Fresno, Bakersfield, and Visalia have groundwater recharge programs to ensure that groundwater will continue to be a viable water supply in the future. Extensive groundwater recharge programs are also in place in the south valley where water districts have recharged several million acre-feet for future use and transfer through water banking programs. The extensive use of groundwater in the San Joaquin Valley has historically caused subsidence of the land surface primarily along the west side and south end of the valley. Groundwater Quality In general, groundwater quality throughout the region is suitable for most urban and agricultural uses with only local impairments. The primary constituents of concern are high TDS, nitrate, arsenic, and organic compounds. The areas of high TDS content are primarily along the west side of the San Joaquin Valley and in the trough of the valley. High TDS content of west-side water is due to recharge of stream flow originating from marine sediments in the Coast Range. High TDS content in the trough of the valley is the result of concentration of salts because of evaporation and poor drainage. In the central and west-side portions of the valley, where the Corcoran Clay confining layer exists, water quality is generally better beneath the clay than above it. Nitrates may occur naturally or as a result of disposal of human and animal waste products and fertilizer. Areas of high nitrate concentrations are known to exist near the town of Shafter and other isolated areas in the San Joaquin Valley. High levels of arsenic occur locally and appear to be associated with lakebed areas. Elevated arsenic levels have been reported in the Tulare Lake, Kern Lake and Buena Vista Lake bed areas. Organic contaminants can be broken into two categories, agricultural and industrial. Agricultural pesticides and herbicides have been detected throughout the valley, but primarily along the east side where soil permeability is higher and depth to groundwater is shallower. The most notable agricultural contaminant is DBCP, a now-banned soil fumigant and known carcinogen once used extensively on grapes. Industrial organic contaminants include TCE, DCE, and other solvents. They are found in groundwater near airports, industrial areas, and landfills. Water Quality in Public Supply Wells From 1994 through 2000, 1,476 public supply water wells were sampled in 14 of the 19 groundwater basins and subbasins in the Tulare Lake HR. Evaluation of analyzed samples shows that 1,049 of the wells, or 71 percent, met the state primary MCLs for drinking water. Four-hundred-twenty-seven wells, or 29 percent, exceeded one or more MCL. Figure 38 shows the percentages of each contaminant group that exceeded MCLs in the 427 wells. 178 DWR - BULLETIN 118

7 Chapter 7 Tulare Lake Hydrologic Region Figure 38 MCL exceedances by contaminant group in public supply wells in the Tulare Lake Hydrologic Region Table 31 lists the three most frequently occurring contaminants in each of the six contaminant groups and shows the number of wells in the HR that exceeded the MCL for those contaminants. Table 31 Most frequently occurring contaminants by contaminant group in the Tulare Lake Hydrologic Region Contaminant group Contaminant - # of wells Contaminant - # of wells Contaminant - # of wells Inorganics - Primary Fluoride 32 Arsenic 16 Aluminum 13 Inorganics - Secondary Iron 155 Manganese 82 TDS 9 Radiological Gross Alpha 74 Uranium 24 Radium Nitrates Nitrate(as NO 3 ) 83 Nitrate + Nitrite 14 Nitrite(as N) 3 Pesticides DBCP 130 EDB 24 Di(2-Ethylhexyl)phthalate 7 VOCs/SVOCs TCE 17 PCE 16 Benzene 6 MTBE 6 DBCP = Dibromochloropropane EDB = Ethylenedibromide TCE = Trichloroethylene PCE = Tetrachloroehylene VOC = Volatile organic compound SVOC = Semivolatile organic compound CALIFORNIA S GROUNDWATER UPDATE

8 Chapter 7 Tulare Lake Hydrologic Region Changes from Bulletin There are no newly defined basins since Bulletin However, the subbasins of the San Joaquin Valley, which were delineated as part of the update, are given their first numeric designation in this report (Table 32). Table 32 Modifications since Bulletin of groundwater basins and subbasins in Tulare Lake Hydrologic Region Subbasin name New number Old number Kings Westside Pleasant Valley Kaweah Tulare Lake Tule Kern County Squaw Valley deleted 5-24 Cedar Grove Area deleted 5-72 Three Rivers Area deleted 5-73 Springville Area deleted 5-74 Templeton Mountain Area deleted 5-75 Manache Meadow Area deleted 5-76 Sacator Canyon Valley deleted 5-77 Rockhouse Meadows Valley deleted 5-78 Inns Valley deleted 5-79 Bear Valley deleted 5-81 Several basins have been deleted from the Bulletin report. In Squaw Valley (5-24) all 118 wells are completed in hard rock. Cedar Grove Area (5-72) is a narrow river valley in Kings Canyon National Park with no wells. Three Rivers Area (5-73) has a thin alluvial terrace deposit but 128 of 130 wells are completed in hard rock. Springville Area (5-74) is this strip of alluvium adjacent to Tule River and all wells are completed in hard rock. Templeton Mountain Area (5-75), Manache Meadow Area (5-76), and Sacator Canyon Valley (5-77) are all at the crest of mountains with no wells. Rockhouse Meadows Valley (5-78) is in wilderness with no wells. Inns Valley (5-79) and Bear Valley (5-81) both have all wells completed in hard rock. 180 DWR - BULLETIN 118

9 Chapter 7 Tulare Lake Hydrologic Region Table 33 Tulare Lake Hydrologic Region groundwater data Well Yields (gpm) Types of Monitoring TDS (mg/l) Groundwater Basin/Subbasin Basin Name Area (acres) Budget Type Maximum Average Levels Quality Title 22 Average Range 5-22 SAN JOAQUIN VALLEY KINGS 976,000 C 3, , WESTSIDE 640,000 C 2,000 1, , PLEASANT VALLEY 146,000 B 3, , KAWEAH 446,000 B 2,500 1,000-2, TULARE LAKE 524,000 B 3, , , TULE 467,000 B 3, , KERN COUNTY 1,950,000 A 4,000 1,200-1,500 2, PANOCHE VALLEY 33,100 C , KERN RIVER VALLEY 74,000 C 3, WALKER BASIN CREEK VALLEY 7,670 C CUMMINGS VALLEY 10,000 A TEHACHAPI VALLEY WEST 14,800 A 1, CASTAC LAKE VALLEY 3,600 C VALLECITOS CREEK VALLEY 15,100 C BRITE VALLEY 3,170 A CUDDY CANYON VALLEY 3,300 C CUDDY RANCH AREA 4,200 C CUDDY VALLEY 3,500 A MIL POTRERO AREA 2,300 C 3, gpm - gallons per minute mg/l - milligram per liter TDS -total dissolved solids CALIFORNIA S GROUNDWATER UPDATE

10 PAGE LEFT BLANK INTENTIONALLY

11 Tulare Lake Hydrologic Region California s Groundwater San Joaquin Valley Groundwater Basin Bulletin 118 San Joaquin Valley Groundwater Basin Kaweah Subbasin Groundwater Subbasin Number: County: Tulare, Kings Surface Area: 446,000 acres (696 square miles) Basin Boundaries and Hydrology The San Joaquin Valley is surrounded on the west by the Coast Ranges, on the south by the San Emigdio and Tehachapi Mountains, on the east by the Sierra Nevada and on the north by the Sacramento-San Joaquin Delta and Sacramento Valley. The northern portion of the San Joaquin Valley drains toward the Delta by the San Joaquin River and its tributaries, the Fresno, Merced, Tuolumne, and Stanislaus Rivers. The southern portion of the valley is internally drained by the Kings, Kaweah, Tule, and Kern Rivers that flow into the Tulare drainage basin including the beds of the former Tulare, Buena Vista, and Kern Lakes. The Kaweah subbasin lies between the Kings Groundwater Subbasin on the north, the Tule Groundwater Subbasin on the south, crystalline bedrock of the Sierra Nevada foothills on the east, and the Kings River Conservation District on the west. The subbasin generally comprises lands in the Kaweah Delta Water Conservation District. Major rivers and streams in the subbasin include the Kaweah and St. Johns Rivers. The Kaweah River is the primary source of recharge to the area. Average annual precipitation is seven to 13 inches, increasing eastward. Hydrogeologic Information The San Joaquin Valley represents the southern portion of the Great Central Valley of California. The San Joaquin Valley is a structural trough up to 200 miles long and 70 miles wide. It is filled with up to 32,000 feet of marine and continental sediments deposited during periodic inundation by the Pacific Ocean and by erosion of the surrounding mountains, respectively. Continental deposits shed from the surrounding mountains form an alluvial wedge that thickens from the valley margins toward the axis of the structural trough. This depositional axis is below to slightly west of the series of rivers, lakes, sloughs, and marshes, which mark the current and historic axis of surface drainage in the San Joaquin Valley. Water Bearing Formations The sediments that comprise the Kaweah Subbasin aquifers are unconsolidated deposits of Pliocene, Pleistocene, and Holocene age. On the east side of the subbasin, these deposits consist of arkosic material derived from the Sierra Nevada and are divided into three stratigraphic units: continental deposits, older alluvium and younger alluvium. In the western portion of the subbasin, near Tulare Lake bed, unconsolidated deposits consisting of flood-subbasin and lacustrine and marsh deposits interfinger with east side deposits. The continental deposits of Pliocene and Pleistocene age are divided into oxidized and reduced deposits based on depositional environment. The Last update 2/27/04

12 Tulare Lake Hydrologic Region California s Groundwater San Joaquin Valley Groundwater Basin Bulletin 118 oxidized deposits, which crop out along the eastern margin of the valley, consist of deeply weathered, poorly permeable, reddish-brown sandy silt and clay with well-developed soil profiles. The reduced deposits are moderately permeable and consist of micaceous sand, silt, and clay that extend across the trough in the subsurface to the west side of the valley. Older alluvium, which overlies the continental deposits, is moderately to highly permeable and is the major aquifer in the subbasin. Younger alluvium consists of arkosic beds, moderately to highly permeable consisting of sand and silty sand. Flood-basin deposits consist of poorly permeable silt, clay, and fine sand. Ground water in the flood-basin deposits is often of poor quality. Lacustrine and marsh deposits consist of blue, green, or gray silty clay and fine sand and underlie the flood-subbasin deposits. Clay beds of the lacustrine and marsh deposits form aquitards that control the vertical and lateral movement of ground water. The most prominent clay bed is the Corcoran clay which underlies the western half of the Kaweah Subbasin at depths ranging from about 200 to 500 feet (DWR 1981). In the eastern portion of the subbasin, ground water occurs under unconfined and semiconfined conditions. In the western half of the subbasin, where the Corcoran Clay is present, ground water is confined below the clay. Land subsidence of up to 4 feet due to deep compaction of fine-grained units has occurred in separate areas of the southern and western portion of the Subbasin (Ireland and others 1984). The estimated average specific yield for this subbasin is 10.8 percent (based on DWR internal data and Davis 1959). Restrictive Structures Groundwater flow is generally southwestward. Small groundwater depressions occurred to the north and south of Visalia and at the subbasin s northwest corner, and a groundwater mound was present in the central western subbasin during 1999 (DWR 2000). Based on current and historical groundwater elevation maps, horizontal groundwater barriers do not appear to exist in the Subbasin. Groundwater Level Trends Changes in groundwater levels are based on annual water level measurements by DWR and cooperators. Water level changes were evaluated by quarter township and computed through a custom DWR computer program using geostatistics (kriging). On average, the subbasin water level has declined about 12 feet from 1970 through The period from 1970 through 1978 showed steep declines totaling about 25 feet. The ten-year period from 1978 to 1988 saw stabilization and rebound of about 50 feet, bringing water levels above the 1970 water level by 25 feet through 1995 again showed steep declines, bottoming out in 1995 at nearly 35 feet below the 1970 level. Water levels then rose about 22 feet from 1996 to 2000, bringing water levels to approximately 12 feet below 1970 levels. Groundwater Storage Estimations of the total storage capacity of the subbasin and the amount of water in storage as of 1995 were calculated using an estimated specific yield of 10.8 percent and water levels collected by DWR and cooperators. Last update 2/27/04

13 Tulare Lake Hydrologic Region California s Groundwater San Joaquin Valley Groundwater Basin Bulletin 118 According to these calculations, the total storage capacity of this subbasin is estimated to be 15,400,000 af to a depth of 300 feet and 107,000,000 af to the base of fresh groundwater. These same calculations give an estimate of 11,600,000 af of groundwater to a depth of 300 feet stored in this subbasin as of 1995 (DWR 1995). According to published literature, the amount of stored groundwater in this subbasin as of 1961 is 34,000,000 af to a depth of < 1000 feet (Williamson 1989). Groundwater Budget (Type B) Although a detailed budget was not available for this subbasin, an estimate of groundwater demand was calculated based on the 1990 normalized year and data on land and water use. A subsequent analysis was done by a DWR water budget spreadsheet to estimate overall applied water demands, agricultural groundwater pumpage, urban pumping demand and other extraction data. Natural recharge is estimated to be 62,400 af. Artificial recharge was not determined for all entities, but Lakeside Irrigation District has recharged about 7,000 af per year and in wet years may recharge up to 30,000 af (Cartwright 2001). There is approximately 286,000 af of applied water recharge into the subbasin. Subsurface inflow was not determined. Annual urban and agricultural extraction is estimated to be 58,800 af and 699,000 af, respectively. Other extractions and subsurface inflow were not determined. Groundwater Quality Characterization. The groundwater in this basin is generally of a calcium bicarbonate type, with sodium bicarbonate waters near the western margin. TDS values range from 35 to 1,000 mg/l, with a typical range of 300 to 600 mg/l. The Department of Health Services, which monitors Title 22 water quality standards, reports TDS values in 153 wells ranging from 35 to 580 mg/l, with an average value of 189 mg/l. Impairments. There are localized areas of high nitrate pollution on the eastern side of the basin. There is also high salinity water between Lindsay and Exeter (Edwards 2001). Water Quality in Public Supply Wells Constituent Group 1 Number of Number of wells with a wells sampled 2 concentration above an MCL 3 Inorganics Primary Radiological Nitrates Pesticides VOCs and SVOCs Inorganics Secondary A description of each member in the constituent groups and a generalized discussion of the relevance of these groups are included in California s Groundwater Bulletin 118 by DWR (2003). 2 Represents distinct number of wells sampled as required under DHS Title 22 program from 1994 through Last update 2/27/04

14 Tulare Lake Hydrologic Region California s Groundwater San Joaquin Valley Groundwater Basin Bulletin Each well reported with a concentration above an MCL was confirmed with a second detection above an MCL. This information is intended as an indicator of the types of activities that cause contamination in a given basin. It represents the water quality at the sample location. It does not indicate the water quality delivered to the consumer. More detailed drinking water quality information can be obtained from the local water purveyor and its annual Consumer Confidence Report. Well Characteristics Well yields (gal/min) Municipal/Irrigation Range: 100 2,500 Average: 1,000 2,000 Total depths (ft) Domestic Municipal/Irrigation Range: Active Monitoring Data Agency Parameter Number of wells /measurement frequency DWR (incl. Cooperators) Groundwater levels 568 Semi-annually Department of Health Services (inc. cooperators) Title 22 water quality 270 Varies Basin Management Groundwater management: Water agencies Public Private Kings County Water District promulgated a Ground Water Management Plan under AB 255 during 1992, and the Kaweah Delta Water Conservation District passed a Ground Water Management Plan under AB 3030 in Exeter I.D., Ivanhoe I.D., Kaweah-Delta Water Conservation District, Kings River Conservation District, Lakeside Irrigation Water District, Lindmore I.D., Lindsay- Strathmore I.D., St. Johns W.D., Tulare I.D., and Stone Corral W.D. California Water Service Visalia; Melga Canal Company; Settlers Ditch Company; Corcoran Irrigation Company. References Cited California Department of Water Resources (DWR), San Joaquin District. Unpublished Land and Water Use Data.. Well completion report files Internal computer spreadsheet for 1990 normal computation of net water demand used in preparation of DWR Bulletin Spring 1999, Lines of Equal Elevation of Water in Wells, Unconfined Aquifer. 1:253,440 scale map sheet Depth to Top of Corcoran Clay. 1:253,440 scale map. Last update 2/27/04

15 Tulare Lake Hydrologic Region California s Groundwater San Joaquin Valley Groundwater Basin Bulletin 118 Croft, MG, and Gordon, GV Geology, Hydrology, and Quality of Water in the Hanford-Visalia Area, San Joaquin Valley, California. USGS Open-File Report. Davis, GH, Green, JH, Olmstead, SH, and Brown, DW Ground Water Conditions and Storage Capacity in the San Joaquin Valley, California. US Geological Survey Water Supply Paper No p. Edwards, Scott A., General Manager, Lindsay-Strathmore I.D Response to DWR questionnaire. February 6. Hendrix, Paul., Engineer Manager, Tulare I.D Response to DWR questionnaire. March 1. Ireland, RL, Poland, JF, and Riley FS Land Subsidence in the San Joaquin Valley, California as of USGS Professional Paper 437-I. Williamson, Alex K, Prudic, David E, and Swain, Lindsay A Groundwater flow in the Central Valley, California. US Geological Survey Professional Paper 1401-D. 127 p. Additional References California Department of Water Resources (DWR) Bulletin California Water Plan Update, Volume Bulletin Ground Water Subbasins in California. Schafer, RL & Associates Written Correspondence. Errata Changes made to the basin description will be noted here. Last update 2/27/04

16 California Water Service 2015 Urban Water Management Plan Visalia District Appendix G: Supplemental Water Supply Information TID-City of Visalia Water Exchange Agreement

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40 California Water Service 2015 Urban Water Management Plan Visalia District Appendix G: Supplemental Water Supply Information City of Visalia Groundwater Impact Fee Memo

41 Job No V1 WATER WASTEWATER STREETS & ROADS STORM DRAINAGE LAND DEVELOPMENT IRRIGATION DISTRICTS AGRICULTURE ENERGY SERVICES 286 W. Cromwell Avenue Fresno, CA FAX To: Michael Olmos, Daniel M. Dooley, City of Visalia From: Richard M. Moss and Laurence Kimura Subject: City of Visalia Groundwater Impact Fee Date: September 9, 2004 Overview and Background Provost & Pritchard Engineers (P&P) has been asked to assist the City staff in preparing an analysis of the conditions affecting the overdraft of groundwater resources beneath the City of Visalia as they relate to the impacts caused by urban and industrial development of agricultural lands typically surrounding the City. City Counsel Dan Dooley outlined potential concepts to further the City s goals in this regard in a memorandum to the City Council on July 9, 2004 (attached). In particular, P&P has been asked to provide an analytical basis for the establishment of a fee to be paid by developers in mitigation of the impacts to groundwater that the City then becomes responsible for implementing. We have attempted herein to lay out a rational basis for such a fee. Dan Dooley s memorandum fairly and succinctly outlines the need for mitigation of groundwater impacts as they relate to the City s land use decisions. It further describes the responsibility of cities and urban water suppliers to assure a long-term sustainable water supply to meet current and future needs of their constituents and the known limitations of groundwater in the region (and as Visalia s only source of supply). His memo however, focuses primarily on the impacts to the groundwater associated with the loss of surface water supplies when conversion from agriculture to urban/industrial land use occurs and water is subsequently sourced only from groundwater. A more thorough review of the impacts to the groundwater balance associated with land use changes reveals impacts to groundwater from additional factors that also need to be considered and mitigated. We will attempt herein to describe and quantify all of these impacts and ways to mitigate the impacts. It is important to remember that a high quality, sustainable supply of groundwater will likely always be the cheapest source of water to meet the City s water needs and thus extraordinary steps need to be taken to protect this resource. Page 1 of 10

42 Land Use and Water Balance In an attempt to let a picture tell a thousand words Figure 1 tries to pictorially describe the generalized components to the water balance for an agricultural setting and an urban/industrial setting including the inflows and outflows to the surface and to groundwater. Virtually all of these water balance factors will change with a changed land use, especially a change as significant as a change from an agricultural land use to an urban/industrial land use. At the risk of further generalization, with a change from agricultural land use to urban/industrial land use, the Evapotranspiration and Consumption of water will decrease; Usable Precipitation also decreases as a result of hardened surfaces and increased storm water runoff; Direct Recharge decreases as a result of piping or lining canals and ditches; Deep Percolation decreases as a result of less surface area being irrigated and less water being applied; in a San Joaquin Valley setting with good quality and quantities of groundwater, Surface Water use is typically eliminated as urban/industrial areas use groundwater almost exclusively; significant quantities of Wastewater are generated and exported outside of the city proper; even though Pumped Groundwater becomes the only source of water for the urban/industrial area, it may or may not show an increase in use over the previously agricultural area depending largely upon the relative volumes of Surface Water and Pumped Groundwater used in the agricultural setting. Changes to Inflow and Outflow to a groundwater basin occur very slowly, as the rate of water movement in the subsurface is extremely slow. Changes in land use can affect the movement of water into and out of a groundwater basin, but the slow movement of groundwater dampens the effect of these changes and renders the changes difficult to quantify without a great deal of modeling and analysis. Impacts to Groundwater with Changes in Land Use In analyzing the effect of land use change on groundwater, we primarily need to concern ourselves with those factors that add or subtract from the groundwater recognizing that the other water balance factors are interrelated with those just affecting groundwater 1. Thus, if we can directly quantify the factors of Deep Percolation, Direct Recharge, Pumped Groundwater, subsurface Inflow and Outflow and Wastewater Treatment Plant Recharge as conditions exist in the agricultural setting and alternatively in the urban/industrial setting, we can gauge the impacts to groundwater associated with the change in land use. Table 1 and Table 2 are compilations of data and calculations regarding each of the water balance factors affecting groundwater in an agricultural setting (Table 1) and an urban setting (Table 2). The majority of this data was obtained from the recent report prepared for the Kaweah Delta Water Conservation District entitled the Water Resources Investigation of the Kaweah Delta Water Conservation District, prepared by 1 You will note that changed Surface Water availability is not a factor to be used in directly determining groundwater impact. The loss of Surface Water availability results in increased use of Pumped Groundwater to the extent that overall demands for water are nearly the same before and after the land use change (and the other factors do not change). Similarly, the reduction in Evapotransporation and water Consumption associated with urban and industrial land use (over that of an agricultural setting) will result in less Pumped Groundwater being used (again, if the other factors remain the same). Page 2 of 10

43 Figure 1. Agricultural to Urban/Industrial Land Use Conversion Impacts on Water Balance and Groundwater Evapo- Transpiration Usable Precipitation Evapo- Transpiration Usable Precipitation Consumption Direct Recharge Surface Water Direct Recharge Wastewater Evaporation Treatment Plant Reclaim To Ag Deep Percolation Direct Recharge Pumped GW Deep Percolation Direct Recharge Pumped GW WWTP Recharge Inflow Groundwater Outflow Inflow Groundwater Outflow An Acre of Agriculture An Acre of Urban/Industrial Development Evapotranspiration is the water to evaporate or transpirate from the land surface as part of growing a crop or from urban landscaping; Usable precipitation is the water available from rainfall which falls on the land that becomes usable for meeting water needs of the land immediately, or subsequently if stored to a recoverable water source (typically groundwater); Direct Recharge is the water applied for the purpose of recharging the groundwater reservoir or which recharges naturally in the delivery of water to the land; Surface Water is water brought to the land via surface delivery (not otherwise available from local groundwater); Deep Percolation is water applied and rainfall in excess of crop or landscape needs which serves to recharge groundwater; Pumped Groundwater is water pumped from the groundwater; Wastewater is water sent to the wastewater treatment plant for treatment and disposal. In the City of Visalia s case, this water is percolated to groundwater down-gradient and outside of the City (WWTP Recharge), delivered for agricultural reuse (Reclaim to Ag) or evaporated from ponds (Evaporation); Inflow/Outflow is water flowing subsurface into and out of the groundwater reservoir. Page 3 of 10

44 Fugro West, Inc. and dated December of 2003 (Fugro West Report). This is the most recent attempt to quantify the water balance and the factors affecting regional water balance. The Kaweah Delta Water Conservation District service area was divided into six hydrologic units and the water balance factors analyzed for each of the units. Figure 2 is taken from the Fugro West Report and shows the boundaries of the six Hydrologic Units. Hydrologic Unit III encompasses the majority of the City of Visalia and its sphere-of-influence. While it was not a perfect fit, the information for Hydrologic Unit III was used as being representative of the water balance in the City of Visalia and its surrounding farmland. The origins of all of the data used in this evaluation are footnoted in the Tables 1 and 2. Groundwater Pumping The relative volumes of groundwater pumped by an agricultural acre of land and an urban/industrial acre are significant water balance factors in determining the net impact to groundwater created by this land use change. It is estimated that an acre of land in agricultural crops pumps on the average 2.57 acrefeet per acre per year in Hydrologic Unit III. Urban and industrial water use is estimated to pump an average across the City of Visalia of approximately 1.88 acre-feet per acre per year. This is actually a net reduction in groundwater use, a positive impact, resulting from the change in land use. There was no effort made to differentiate between different kinds of development, i.e. heavy or light residential, industrial, etc. However, there may be reason to differentiate given the amount of water used by the different urban/industrial land uses are significant. Deep Percolation There are two sub-components to Deep Percolation to groundwater that are estimated herein: (i) percolation resulting from the application of irrigation water in excess of crop or landscaping needs, resulting in water movement through the soil profile beyond the root zone to accrual in the groundwater, and (ii) percolation of rainfall that falls on the land and, as well, moves beyond being available for plants or landscaping use to accrual in the groundwater. The average Deep Percolation flow to groundwater for the agricultural land use setting is estimated to be 1.26 acre-feet per acre per year in Hydrologic Unit III. The average Deep Percolation flow to groundwater for the urban/industrial land use setting in Hydrologic Unit III is estimated to be 0.28 acre-feet per acre. Thus, there is estimated to be a net negative impact to groundwater associated with the agricultural to urban/industrial land use change as it relates to the effective recharging of the groundwater associated with Deep Percolation of irrigation water and precipitation. Direct Recharge Direct Recharge within Hydrologic Unit III occurs from three primary sources, (i) recharge associated with the flow of water in the Kaweah and St. John s Rivers, (ii) recharge from ditches and natural waterway losses associated with the delivery of surface water for irrigation, and (iii) surface water that is placed into recharge basins. The primary change in Direct Recharge seen when agricultural lands are converted to urban/industrial land uses occurs when ditches and natural waterways are piped or concrete lined. It has been estimated that 20 percent of the ditches and waterways are being covered over or eliminated as a results of urbanization and thus we have estimated the volume of Direct Recharge associated with ditches and natural waterways for Hydrologic Unit III to be reduced by 20 percent on an acre-foot per acre basis. Direct recharge in an agricultural setting is estimated to be 0.28 acre-feet per Page 4 of 10

45 Figure 2. Fugro West Report Hydrologic Units Page 5 of 10

46 acre. Direct recharge in an urban/industrial setting is estimated to be 80 percent of the agricultural setting amount or 0.22 acre-feet per acre. Direct recharge associated with surface water placed into recharge basins and flow in the Kaweah and St. John s Rivers is assumed to remain unchanged with the conversion of agricultural lands to urban/industrial uses. Thus, there is estimated to be a net negative impact to groundwater associated with the agricultural to urban/industrial land use change as it relates to the effective recharging of the groundwater associated with Direct Recharge of surface water. Net Balance - The net balance or net impact to groundwater associated with agricultural land use in Hydrologic Unit III is estimated to be a negative impact of 1.03 acre-feet per acre per year (Table 1). The net negative impact to groundwater with the urban/industrial uses in the City of Visalia is estimated to be 1.22 acre-feet per acre (Table 2). Thus, there is a net increase in the negative impacts to groundwater of 0.19 acre-feet per acre associated with the change in land use of agricultural use to urban/industrial use. It should be noted that the recharge associated with flows to groundwater from the wastewater treatment plant are considered to be exported outside of the City and thus do not accrue to benefit the groundwater beneath the City. In fact, the water build-up or mound created by the intentional and constant percolation at the wastewater treatment plant will likely become a problem resulting in additional acreage being purchased for disposal of wastewater. Mitigation of Groundwater Impacts and Calculation of a Groundwater Impact Fee There are a number of ways to mitigate the impact to the groundwater associated with a land use change from agriculture to urban/industrial within the City of Visalia. It is believed that the least expensive and easiest implemented mitigation would be to develop additional Direct Recharge capability within the City. This would include purchasing rights to surface water available on the Kaweah or St. Johns Rivers system and to have that surface water delivered to recharge basins constructed within the City or immediately up-gradient from the City. Alternatives, which have not been analyzed as part of this study, would include the purposeful reduction in urban water demand by the use of water conservation and/or water reclamation practices, including low flow plumbing fixtures, waste water treatment/reuse for urban landscaping and/or new standards for reduced water use on urban landscaping. Table 3 is a spreadsheet analysis of the initial capital costs and subsequent annual costs associated with the Direct Recharge alternative for mitigation of groundwater impacts. Preliminary estimates have been made as to the cost of purchasing surface water rights and the construction of recharge basins. Additionally the annual costs associated with the delivery of the surface water and the operation and maintenance of the basins has been estimated. The recharge basins need to be located to minimize construction costs for water delivery, over lands that are conducive to recharge, and over lands that will serve to optimize the recharge value to the groundwater immediately underneath the City of Visalia. Depending upon location, there is also a potential for these basins to provide storm water layoff benefits so that the City could continue use local ditches and waterways to dispose of storm water. However, new recharge basins probably do not significantly reduce the need for new storm water detention or retention basins within the city. Similarly, the better locations for the recharge basins may or may Page 6 of 10

47 not work for conjunctively using them to provide recreational or open-space benefits. That is not to say that such multipurpose benefits should not be pursued, but that it may not necessarily reduce the cost of developing the additional recharge capability needed to mitigate the impacts to the groundwater of development. An input into the spreadsheet is the amount of water to be recharged annually. This is the resultant of the net increase in negative impact to groundwater associated with the agriculture to urban/industrial land use change (as calculated previously, 0.19 acre-feet per acre developed) added to a pro rata share of the existing and persistent long-term overdraft in and around Visalia. The Fugro West Report estimates overdraft in Hydrologic Unit III using the Specific Yield Method of analysis as 3,100 acre-feet over 35,457 total acres or 0.09 acre-feet per acre. Thus, the total volume to be replaced annually is estimated to be 0.28 acre-feet per developed acre. This water impact volume drives how many sinking basin acres will be needed, how much surface water needs to be purchased and ultimately the total groundwater impact fee. With all of the estimates and assumptions imbedded in the spreadsheet analysis, we estimate a groundwater impact fee of approximately $1,589 per developed acre is needed. Alternatively, you may wish to consider spreading and collecting just the annual cost components of water purchase and recharge basin operations over the actual volumes of water pumped to serve the new developments. Using the estimate of average annual volume of groundwater pumped of 1.88 acre-feet per acre this would equate to a charge of $5.28 per acre-foot of groundwater pumped. This would also serve to reduce the initial groundwater impact fee to $1,391 per developed acre. Summary An analysis and a methodology to calculate and mitigate the impact to groundwater associated with the change in land use from agriculture to urban/industrial uses have been proposed. Undoubtedly, as with any such analysis, refinements could be made to it to be more exacting. However, there is no question that there is a long-term groundwater overdraft in and around the City of Visalia as evidenced by the lowering levels to groundwater as monitored and recorded monthly by the California Water Service Company. Collection and dedication of monies to offset the negative impacts of agriculture to urban/industrial land use change and the pro rata share of the existing groundwater overdraft is a very good step in addressing this issue. Page 7 of 10

48 Table 1. City of Visalia Groundwater Impact Fee - Water Basis Estimate of Agricultural Impacts to Groundwater Data/Assumptions: Hydrologic Unit III = 35,457 acres (Fugro 2003 Table 1) Ag acres = 21,493 acres (Fugro 2003 Table 55) Percolation of Irrigation Water = 18,202 acre-feet (Fugro 2003 Table 55) Percolation of Rainfall = 8,779 acre-feet (Fugro 2003 Table 55) Irrigated Ag GW pumping = 55,300 acre-feet (Fugro 2003 Table 73) Conveyance Losses = 6,705 acre-feet (Fugro 2003 Table 22) Calculations: GW pumping = 55,300/21,493 = 2.57 acre-feet/acre Deep Percolation Percolation of Irrigation Water = 18,202/21,493 = 0.85 acre-feet/acre Percolation of Rainfall = 8,779/21,493 = 0.41 acre-feet/acre Direct Recharge Conveyance Losses = 9,862/35,457 = 0.28 acre-feet/acre Net Balance: Withdrawal Ag GW Pumping Input Deep Percolation Percolation of Irrigation Water Percolation of Rainfall Input Direct Recharge Conveyance Losses Net Balance acre-feet/acre 0.85 acre-feet/acre 0.41 acre-feet /acre 0.28 acre-feet/acre acre-feet/acre References: Fugro, Water Resources Investigation of the Kaweah Delta Water Conservation District, Final Report, December 2003 Page 8 of 10

49 Table 2. City of Visalia Groundwater Impact Fee - Water Basis Estimate of Urban/Industrial Impacts to Groundwater Data/Assumptions Hydrologic Unit III = 35,457 acres (Fugro 2003 Table 1) Urban acres = 14,106 acres (Boyle 2003) Average Day Flow = 16, gpm (Boyle 2003) Landscape/Turf area = 35% of developed area (CH2M Hill 1992) Landscape Deep Percolation = 15% of applied water (CH2M Hill 1992) Urban Precipitation Deep Percolation = 20% of infiltration, Infiltration = 60% of precipitation (CH2M Hill 1992) Landscape/Turf Irrigation Return = 10% of applied water, 4.5 AF per year applied (CH2M Hill 1992) Average Rainfall = 10.9 inches (Fugro 2003 Table 73) Conveyance Losses = 9,862 acre-feet (Fugro 2003 Table 22) Assume 20% of open channels are piped, therefore 20% loss of conveyance seepage (Keller communication/review of recent experience) Assume runoff on urban area is pumped and disposed outside of City Calculations GW pumping = ((16,489/449)*(1.983*365))/14,106 = 1.88 acre-feet/acre Deep Percolation Landscape Deep Percolation = ((14,106*0.35)*4.5*0.15)/14,106 = 0.24 acre-feet/acre Landscape Rainfall Deep Percolation = (10.9/12)*0.6*0.2*14,106*0.35/14,106 = 0.04 acre-feet/acre Direct Recharge Landscape Irrigation Return = 14,106*0.35*4.5*0.1/14,106 = 0.16 acre-feet/acre Conveyance Losses = 80% of Ag rate = 0.80*9,862/35,457 = 0.22 acre-feet/acre Net Balance Withdrawal Urban GW Pumping Input Deep Percolation Percolation of Landscape Percolation of Rainfall Input Direct Recharge Landscape Irrigation Return Conveyance Losses Net Balance acre-feet/acre 0.24 acre-feet/acre 0.04 acre-feet/acre 0.16 acre-feet/acre 0.22 acre-feet/acre acre-feet/acre References: Boyle, Draft Final Report - Water Supply and Facilities Master Plan Executive Summary, 2003 CH2M Hill, Fresno/Clovis Metro Water Resources Management Plan, Phase I Report, Jan 1992 Fugro, Water Resources Investigation of the Kaweah Delta Water Conservation District, Final Report, December 2003 Page 9 of 10

50 Table 3. City of Visalia Groundwater Impact Fee - Cost Basis Purchase and Direct Recharge of Groundwater Indicates Input Variables Analysis Control Variables Average Number of Days Kaweah River Water is Available Groundwater Recharge Rate Volume of Water to be Recharged Annually Basin Land Use Efficiency Conveyance Losses to City Boundary Recharge Facility Requirements Net Acreage of Recharge Facilities Gross Acreage for Recharge Facilities Recharge Water Volume Requirements Headgate Entitlement Required Indicates Calculated Values 145 days per year 0.25 af per basin acre per day 0.28 af per acre developed per year 85 percent 33 percent acres per acre developed acres per acre developed af per acre developed per year Cost Control Variables Capital Costs Land Cost Surface Water Entitlement Capital Cost Recharge Basin Construction Cost Turnout Facility Cost Construction Related Engineering, Legal, & Contingencies Annual Costs Recharge Basin Annual Maintenance Costs Maintenance Operation Surface Water Delivery Annual Costs Volume of Groundwater Pumped Annually for Urban Use Term of Annual Cost Recovery Capital Cost Components Recharge Facilities Land Purchase Cost Surface Water Entitlement Purchase Cost Recharge Facilities Construction Cost Total Water Purchase and Recharge Facilities Capital Costs Annual Cost Components Recharge Facilities Operation and Maintenance Surface Water Delivery Costs Total Annual Costs Total Annual Costs Spread Over Groundwater Pumped Present Value of Annual Cost Components (Assumes inflation of Annual Cost Components is equal to the City's internal discount rate) Impact Fee Total $65,000 per acre $1,500 per acre-foot $20,000 per basin acre $5,000 per basin acre 25 percent $200 per basin acre per year $10 per acre-foot $15 per acre-foot 1.88 af per acre 20 years $591 per acre developed $559 per acre developed $241 per acre developed $1,391 per acre developed $4.34 per acre developed per year $5.59 per acre developed per year $9.93 per acre developed per year $5.28 per acre-foot pumped per year $199 per acre developed $1,589 per acre developed Page 10 of 10