USDA: Lake Waco/Bosque River Initiative. Future Growth Projections for the Lake Waco/Bosque River Watershed

Transcription

1 USDA: Lake Waco/Bosque River Initiative Future Growth Projections for the Lake Waco/Bosque River Watershed Nancy Easterling WP0005 May 2000 Texas Institute for Applied Environmental Research Tarleton State University Box T0410 Tarleton Station Stephenville, Texas FAX

2 Acknowledgements The research on which this report is based was financed by the U.S. Department of Agriculture, Natural Resources Conservation Service. Dr. Larry Hauck, Assistant Director of Research at TIAER, provided guidance and insight in preparing this document. Representatives from cities in the Bosque River watershed met on several occasions to review material needed for this report and provided important feedback. Don Gosdin, Artist Illustrator at TIAER, prepared the map in Figure 1. Tommie Nielsen, former Research Assistant at TIAER, calculated the historical number of cows in Erath and Hamilton counties using milk production data. 2

3 Abstract The Texas Institute for Applied Environmental Research (TIAER) completed future growth projections for the USDA Lake Waco-Bosque River Initiative. A twenty year planning horizon was selected as appropriate for future growth estimates of potential pollution sources in this central Texas watershed. Sectors for which future growth was estimated include wastewater treatment plants (WWTPs), dairy farms, urban growth, and row crops. These sectors represent the watershed s major potential contributors of phosphorus, the pollutant of concern in the Bosque River watershed. Texas Water Development Board estimates of future population growth served as the basis for growth projections of WWTP discharge and urban population. Regression equations based on historical milk production records enabled growth projections for cows in the watershed. Estimates of row crop acreage were based on geographic information system analysis of changes in historical thematic satellite images. Regulatory limits exist for WWTP effluent and dairy cow numbers. The currently permitted maximum amounts of wastewater effluent and dairy cows in the watershed were found to be greater than growth estimates for the year Urban population growth is estimated to increase by 31 percent while row crop production is not expected to increase by the year To accommodate additional growth in the watershed, notably in the municipal and industrial areas, an allotment of 10 percent of the current WWTP discharge is projected. These projections will be used in the modeling efforts and other analyses for the USDA Lake Waco/Bosque River Initiative. 3

4 4

5 Contents Future Growth Projections for the Lake Waco/Bosque River Watershed Introduction Planning Horizons for Future Growth Projections Urban NPS/Population Projections Wastewater Treatment Plant Effluent Projections Projections of Dairy Cow Population in the Bosque River Watershed Method Used to Determine Historical BRW Cow Numbers Method Used to Estimate Current BRW Cow Population Method Used to Predict BRW Cow Numbers Projections of Row Crop Production in the Bosque River Watershed Projections of Unallocated Municipal/Industrial Contributions to the Bosque River Watershed Summary References Appendix A. City of Waco Population and WWTP Projections for the BRW Area Appendix B. WWTP Effluent Projection Calculations Appendix C. Additional Details of Determining Cow Numbers

6 Future Growth Projections for the Lake Waco/Bosque River Watershed 6

7 Tables Table 1: Population Projections, Revisions and Projected Growth Table 2: Daily Average BRW WWTP Discharge Limits Table 3: Estimated Number of Cows in Erath and Hamilton Counties, Table 4: Estimated Number and Annual Growth Rate of BRW Cows in Erath and Hamilton Counties, Table 5: Estimated Number of BRW Cows, Table 6: Projected BRW Cow Numbers Based on Regression Equation Table 7: Changes in BRW Row Crop Acres, 1977 to Table 8: Summary of Future Growth Projections for the BRW Table A-1: WWTP Effluent Discharge Projections for the City of Waco Located in the BRW Table B-1: Population Growth Rate Calculations Table B-2: WWTP Discharge Projections Table C-1: Figures Used in Estimating the Number of BRW Cows in

8 Future Growth Projections for the Lake Waco/Bosque River Watershed 8

9 Figures Figure 1: The Bosque River Watershed and Lake Waco Figure 2: Graph and Regression Equation of Estimated BRW Cow Numbers, Figure 3: Graph and Regression Equation of Estimated BRW Cow Numbers,

10 Future Growth Projections for the Lake Waco/Bosque River Watershed 10

11 Future Growth Projections for the Lake Waco/Bosque River Watershed Introduction The North Bosque River, which flows approximately 125 miles from Erath county, Texas, to Lake Waco, has been included for several years on the Clean Water Act section 303(d) list of impaired water bodies. The river is comprised of two segments, 1226 and 1255, which have been classified by the Texas Natural Resource Conservation Commission (TNRCC). Both segments are cited for nutrient enrichment and other pollutants. The Texas Institute for Applied Environmental Research (TIAER) at Tarleton State University is working with the Bosque River Advisory Committee (BRAC) to consider control or reduction in nutrient loadings in the North Bosque River and to Lake Waco. The research and stakeholder process is occurring through a USDA-funded project entitled the Lake Waco/Bosque River Initiative (USDA Initiative). Factors that can contribute pollutant loads to the system are examined in the USDA Initiative. An important, though difficult, factor in assessments and allocations of nutrient loadings is future contributions. Future contributions are typically estimated by observing historical growth trends in sources and projecting them into the future. Projections of future growth are by definition inexact, with the more distant projections typically representing less accurate estimates. Projections of 20 years are often made, which is the horizon used for future growth projections for the USDA Initiative. Due to concerns about the holistic nature of a watershed s response to environmental influences, the BRAC decided to include the entire Bosque River watershed (BRW) in the future growth projections. This added segment 1246 (the South and Middle Bosque watersheds) and segment 1225 (Lake Waco). Figure 1 shows the cities, major rivers and boundaries of the BRW. The USDA Initiative addresses elevated levels of phosphorus. Data from years of research in the Bosque River watershed indicate that phosphorus is the nutrient that limits (or controls) growth of aquatic plants in the Bosque River watershed. Long term TIAER studies indicate that orthophosphate phosphorus (PO 4 -P) has a stronger statistical relationship with aquatic plant growth in the North Bosque River than does total phosphorus, the other common form of phosphorus measured in the Bosque River system. 11

12 Future Growth Projections for the Lake Waco/Bosque River Watershed Anthropogenically derived sources of PO 4 -P in the watershed include urban nonpoint source runoff, wastewater treatment plants (WWTPs), dairy operations, and row crop production. Effluent from manufacturing and industrial facilities in the watershed is received and treated by local WWTPs. No industrial producers are permitted to independently discharge wastes into the watershed. In addition to wastewater treatment plants and dairies, four other facilities in the Bosque River watershed hold TNRCC permits to dispose of wastes. These facilities include a limestone manufacturing facility, a milk products plant, a small mobile home park and a livestock auction barn. Because these four facilities have no discharge permits and do not represent major potential sources of phosphorus, they are not included in the projections of future contributions of phosphorus. The purpose of this paper is to project future growth of anthropogenic sources that are being considered in phosphorus loading considerations within the USDA Initiative. The future growth projections will be used in the computer model simulations as part of the evaluation process of the project. The conclusions presented in this paper have been agreed to by the BRAC. Figure 1: The Bosque River Watershed and Lake Waco 12

13 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections Planning Horizons for Future Growth Projections To provide a basis for future growth projections, a planning horizon must be determined. Often a 20-year planning horizon is used by TNRCC in their wasteload (point source) allocation process. The planning horizon should encompass a reasonable period in which to achieve the desired endpoints (in-stream water quality) and provide ample allowance for future growth to provide for protection of in-stream designated uses in the future. For the USDA Initiative, a 20-year planning horizon was selected. The bases of this 20-year time frame are the following: (1) reduction of elevated phosphorus levels on fields receiving dairy wastes can be a multi-year process and 20 years should provide for substantial reductions in soil phosphorus on these application fields, and (2) this time period represents a reasonable and often used compromise between a projection extending too far into the future and a shortsighted planning horizon which is invalidated by future growth before the endpoints are achieved. Urban NPS/Population Projections Estimates of future population are used to predict urban nonpoint source (NPS) pollution as part of computer modeling efforts. The Texas Water Development Board (TWDB) estimates future population growth for cities and communities throughout Texas in order to predict changes in demand for water. A detailed description of the process used by TWDB to estimate population growth can be found at The mayor, utilities director, and/or other representatives from each of the eight BRW cities were asked to review and provide input on the TWDB population projections. The cities of Clifton and Stephenville submitted revised projections to the BRAC; these revisions have also been submitted to the TWDB. The City of Hico submitted revised population projections to the BRAC based on growth in number of electric meter connections. The City of Waco, only part of which is located within the BRW, provided growth estimates for the BRW portion of its population. Table 1 shows the population estimates for BRW cities for the years 2000, 2010 and

14 Future Growth Projections for the Lake Waco/Bosque River Watershed Table 1: Population Projections, Revisions and Projected Growth City 2000 Populationa 2010 Population 2020 Population Growth Rate ( ) Cliftonb 3,557 3,961 4,268 20% Crawford % Hicob 1,380 1,400 1,417 3% Iredellc % McGregor 5,228 5,670 5,845 12% Meridian 1,504 1,603 1,791 19% Stephenvilleb 16,060 18,638 21,103 31% Valley Mills 1,090 1,107 1,118 3% Wacob,d 34,494 40,965 47,435 38% TOTAL 64,413 74,505 84,190 31% a. Projections were developed by TWDB, except as noted b. Estimates were provided by city representatives c. Estimates for Iredell, not available from TWDB, are based on 1998 Texas Almanac population and TWDB s non-urban growth rate for Bosque county. d. Estimates for the part of Waco within the Lake Waco drainage area; additional details of Waco s population projection are found in Appendix A. Wastewater Treatment Plant Effluent Projections TNRCC records indicate that only municipal wastewater treatment plants (WWTPs) are permitted to discharge in the Bosque River watershed; no industrial facilities hold permits to discharge wastes in the BRW. Estimates of future WWTP effluent are used to predict point source pollution as part of computer modeling efforts. WWTPs are limited by regulation as to the volume of effluent that may be discharged daily and the concentration of key constituents in that effluent. Wastewater discharge is related to the number of people and industrial and manufacturing entities that use the system. The population projections presented in Table 1 were used to estimate the changes in wastewater discharge in the BRW. WWTP effluent from the city of Waco is discharged downstream of BRW and Lake Waco into the Brazos River basin. Waco s effluent thus does not impact the amount of WWTP effluent in the BRW. Several residential developments are expected within the City of Waco s jurisdiction, but are located outside present wastewater collection systems. The City of Waco has already committed funding to connect these planned developments to collection systems that will transport the wastewater out of the 14

15 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections watershed to the treatment facility for the City of Waco. Presently it is unlikely that package wastewater treatment plants will be required at these developments. If package wastewater treatment plants are required, they will not be used beyond the year 2002, according to City representatives. Details of potential package WWTPs for Waco are presented in Appendix A. The TNRCC issues permits to WWTPs, designating a daily average effluent discharge limit. Table 2 shows the daily average discharge limit, in million gallons per day (MGD), for each of the eight permitted WWTPs in the BRW. Each WWTP submits to the TNRCC monthly discharge data, including an average of the measured daily discharges for that month. The monthly averages of daily discharges for each WWTP were averaged for the period January 1997 through December 1998 to obtain a daily average discharge for each WWTP. Daily average discharges are shown beside the TNRCC permit flow limit in Table 2. Table 2: Daily Average BRW WWTP Discharge Limits Recent Average Discharges and Estimated 2010 and 2020 Discharges WWTP Facility Daily Avg Discharge Limita (MGD) Recent Daily Average Dischargeb (MGD) Estimated Discharge in 2010 c (MGD) Estimated Discharge in 2020c (MGD) 2020 Discharge as Portion of Discharge Limit Cliftond % Crawford % Hico % Iredell % McGregor % Meridiane % Stephenville % Valley Mills % TOTALf % a. From TNRCC wastewater discharge permits b. Based on self-reporting flow data from 1997 to 1998 c. Based on estimates of population growth rates in Table 1, applied beginning in d. Clifton s discharge limit represents a requested amendment from the current MGD e. Meridian expects a large increase in industrial use f. Total does not include a potential WWTP for Cranfills Gap, which is not permitted and which would impact the 2020 total MGD by less than one percent; see Appendix B for more details The percentage growth projected for each city (Table 1) was applied to that city s wastewater treatment plant effluent, except as noted, in order to predict WWTP efflu- 15

16 Future Growth Projections for the Lake Waco/Bosque River Watershed ent discharge in 2010 and Appendix B contains details of the growth projections for wastewater treatment plant effluent. The TWDB currently projects decreased water use throughout Texas, especially for industrial water users, due to the development and increasing use of water saving devices. Basing future WWTP effluent on changes in water use, in addition to future population growth, would have produced lower effluent projections. In order to allow sufficient growth potential for WWTPs serving BRW municipalities, projections of future WWTP effluent were based on percentage increases in population. City representatives reviewed the WWTP projections and provided input. The city of Clifton is in the process of building a new wastewater treatment plant, and the figures for Clifton reflect the proposed permit limits. The city of Meridian anticipates industrial growth in their region, and therefore had larger estimates than those based on population increases alone. The WWTP effluent projections for 2010 and 2020 are shown in Table 2. In addition, the discharge projected for 2020 is shown in Table 2 as a percentage of the current regulatory discharge limit. For future effluent projections, the greater of the projected WWTP discharge and the permitted WWTP discharge limit should be used. According to these projections, none of the WWTPs in the BRW will exceed their TNRCC permit limit by Therefore, the WWTP effluent projection used will be each WWTP s permitted daily average discharge, which totals MGD. Projections of Dairy Cow Population in the Bosque River Watershed Dairy farming is a major industry in the BRW, potentially contributing a large proportion of the nutrient loading to Lake Waco. Change in the number of dairy cows in the watershed constitutes an important part of future growth projections. Projection of the future BRW dairy cow population is based on the assumption that future growth will proceed at the same rate as previous growth. Analysis of historical cow numbers can be used to produce a regression equation which describes the past growth rate and can be used to predict future growth. The projection estimate requires the following basic steps: (a) determination of historical numbers of BRW cows, (b) determination of the current number of BRW cows, (c) calculation of a regression equation based on historical cow numbers, and (d) application of the equation to the current number of BRW cows for the desired number of years in the future. Neither the historical BRW cow numbers nor the current BRW cow population are available. Estimates of these two data sets were derived from existing data, as explained below. 16

17 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections Method Used to Determine Historical BRW Cow Numbers The best available source of long term data on BRW cow numbers is milk production data published monthly in The Milk Market Administrators Report. Cow numbers were estimated by dividing the total pounds of milk produced in the month by the average pounds produced per cow per day (55 pounds of milk per cow per day, according to The Milk Market Administrators Report guidelines) then dividing by the number of days in the month. This approximates the number of lactating cows, which is multiplied by the commonly accepted value of 1.2 to approximate total herd size (lactating and dry cows). See Appendix C for details on this calculation. The cow numbers calculated for each month were averaged to produce the mean number of cows for each year of record. It should be noted that the number of cows on individual dairies fluctuates from day to day and season to season. Therefore, a goal of determining exact cow numbers is not appropriate and is superseded by efforts to estimate average numbers of cows. Milk production data are recorded by county rather than by watershed. Because all but two BRW dairies are located in Erath and Hamilton counties, milk production figures for those two counties were used to estimate the cow population in past years. While reliable milk production data are available for Erath county since at least 1980, complete data for Hamilton county are available only since For this study, 1998 is the latest year with a complete set of data. Table 3 shows the estimated number of cows in both counties, as calculated from milk production data for the period of interest. Table 3: Estimated Number of Cows in Erath and Hamilton Counties, Year # Cowsa Year # Cowsa , , , , , , , , , , , , , ,939 a. Based on milk production data from The Milk Market Administrators Report Many Erath and Hamilton dairies are located outside the BRW in adjacent watersheds, so it was necessary to determine the percentage of the counties cows located within the BRW. This was accomplished by dividing the estimated number of cows in the watershed in 1998, excluding the two dairies outside Erath and Hamilton counties, by the 1998 total for both counties. The number of BRW cows in Erath and Hamilton counties during 1998 was estimated, as explained in the next section, to be 17

18 Future Growth Projections for the Lake Waco/Bosque River Watershed 39,938. This number was divided by the 1998 total number of Hamilton and Erath county cows (97,939, shown in Table 3) to yield the percentage of Hamilton and Erath county cows which are located in the BRW (40.8 percent). While this approach assumes that cows in the BRW represent a constant portion of Erath and Hamilton county cows for each year, there exist insufficient data to make any other assumption. The calculated percentage (40.8 percent) was multiplied by the number of Erath and Hamilton cows for each year of record (from Table 3) to estimate historical numbers of BRW cows in Erath and Hamilton counties. These yearly estimates are presented in Table 4, with the annual growth rate in number of cows. Table 4: Estimated Number and Annual Growth Rate of BRW Cows in Erath and Hamilton Counties, Year Erath & Hamilton Countiesa (# cows) BRW (# cows)b Annual Growth Rate ,733 12, ,648 13,721 6% ,049 16,332 19% ,147 20,857 28% ,068 24,087 15% ,474 27,107 13% ,775 27,638 2% ,412 29,529 7% ,437 33,209 12% ,050 37,537 13% ,644 38,595 3% ,289 40,896 6% ,290 39,266-4% ,939 39,938 2% a. Based on data from The Milk Market Administrator s Report b. Calculated from estimated percentage of Erath and Hamilton cows in the BRW in 1998 (40.8%) Method Used to Estimate Current BRW Cow Population Estimating the current number of cows in the BRW required combining data from different sources. First, all operating dairies in the watershed were identified using a list 18

19 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections of dairy addresses compiled by the Texas Department of Health (TDH) for each county, a detailed map of the watershed boundaries, and a considerable amount of ground-truthing. The resulting list of BRW dairies was used to search recent TNRCC dairy inspection reports, which include the actual number of cows present on the inspected dairy. Over one-third of all BRW dairies, however, did not have recent TNRCC inspection reports. TNRCC permits for concentrated animal feeding operations (CAFOs) cannot be used to estimate actual cow numbers because most dairies have fewer cows than the maximum listed on their permit and not all dairies are required to have a permit. (Prior to 1995, dairies with fewer than 250 cows were not required to have a permit; in 1995, that number was lowered to 200 cows.) Therefore, the actual number of cows on any BRW dairy not recently inspected had to be estimated. The percentage of actual cows out of the total allowable number of cows on inspected dairies was calculated and applied to the maximum allowable on the uninspected dairies. The following steps outline the procedure used to estimate cows on uninspected dairies: (1) The number of cows actually present on the dairies inspected from 1997 through 1999 was totaled, using TNRCC inspection reports. The maximum allowable number of cows on those dairies was also totaled. TNRCC CAFO permits provided the maximum allowable number for dairies with permits. For unpermitted dairies, the maximum allowable number of cows was assumed to be either 199 or 249, depending on initial date of operation. The percentage of actual cows out of allowable cows was calculated for the inspected dairies. (2) To estimate the number of actual cows on the uninspected dairies, the percentage calculated above was multiplied by the maximum allowable number of cows for each uninspected dairy. Table 5 presents the data used in estimating the number of BRW cows in The first row of figures in the table presents data for BRW dairies in Erath and Hamilton counties inspected by TNRCC from 1997 through The maximum allowable number of cows was totaled for the 65 inspected dairies. This number had to be adjusted to accommodate dairies located on the boundary between the Bosque and adjacent watersheds. Because some TNRCC permits list total head while other permits list milking head, the figures were also adjusted to represent total cows on all permitted dairies. Appendix C provides details for allocation of cows on the borderline dairies and for adjusting numbers to reflect total cows. The actual number of cows on the first row (27,289) represents the sum from the inspection reports of the 65 inspected dairies, with cow numbers on borderline dairies being appropriately adjusted. Dividing the total of actual cows on those dairies (27,289) by the adjusted maximum number (42,527) yields 64.2 percent. This percentage was applied to the maximum number of cows allowed on the uninspected BRW dairies to estimate their actual cow numbers (second row of Table 5). Four BRW dairies are no longer operating, yet remain on TNRCC s list of permitted dairies. Because they could legally resume operation, they are included in the total for maximum allowable cows. Cow numbers for the two BRW dairies located outside Erath and Hamilton counties, both of which had been inspected, were added to the numbers for the watershed. Recent review of TNRCC permit files show that from January-August 1999, TNRCC issued 19

20 Future Growth Projections for the Lake Waco/Bosque River Watershed permits for one new and two enlarged dairies, adding 1,290 more cows to the total allowable maximum. Although other numbers reflect 1998 conditions, the BRAC decided to include these new cows into the total in order to more accurately reflect the number of cows currently permitted/allowed in the BRW. Table 5: Estimated Number of BRW Cows, 1998 Type of Dairy Maximum Allowable Number of Cowsa Adjusted for Basin & Total Number of Cowsb Actual Number of Cows Actual Compared to Maximum Allowable Inspected BRW dairies in Erath & Hamilton counties Uninspected BRW dairies in Erath & Hamilton counties Out of business permitted dairiesc 42,062 42,527 27, % 22,660 19,712 12,649 2,495 2,495 0 Total in Erath and Hamilton counties 67,217 64,734 39,938 Outside Erath & Hamilton counties 1,050 1, Permitted additions (September 1999) 1,290 1,290 0 Total BRW cows 69,557 67,074 40,483 a. Maximum allowable refers both to TNRCC permit limits and the maximum allowable for unpermitted dairies b. Adjustments include standardizing to total cow numbers and apportioning cows on dairies located only partially within the BRW c. Dairies that are no longer in operation but that are still included on TNRCC s list of permitted dairies. Method Used to Predict BRW Cow Numbers The prediction of BRW cow numbers is based on the application of a regression equation, which describes historical growth in BRW cow numbers, to the current estimated BRW cow population. Estimates of BRW cow populations from 1985 through 1998 were analyzed to produce a regression equation that describes the growth rate from 1985 through A graph of the data (Figure 3) shows a flattening of the growth rate from 1994 through In order to estimate future growth in the BRW cow population, the best information from dairy operators on the BRAC indicated that the more recent flattened trend (Figure 3) is a better representation of expected future growth. The BRAC decided that the projected number of cows based on the regression equation was a more realistic estimate because the earlier period represents an especially dramatic period of growth in the BRW dairy industry which is not likely to be duplicated. 20

21 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections Figure 2: Graph and Regression Equation of Estimated BRW Cow Numbers, Note: Does not include the two dairies located outside of Erath and Hamilton counties 50,000 45,000 40,000 Number of Cows 35,000 30,000 25,000 20,000 15,000 10,000 5,000 y = (x-1985)+13, Figure 3: Graph and Regression Equation of Estimated BRW Cow Numbers, Note: Does not include the two dairies located outside of Erath and Hamilton counties 41,500 41,000 40,500 Number of Cows 40,000 39,500 39,000 38,500 38,000 37,500 y = (x-1994) +38,152 37, The regression equation can be used to calculate future numbers of cows (y) from an initial number of cows plus the product of the desired year in the future (x) and a 21

22 Future Growth Projections for the Lake Waco/Bosque River Watershed coefficient derived from analysis which represents growth per year. The terms of the equation are written in the order shown in the equations in Figures 2 and 3. The future growth equation based on BRW data is as follows: y= (x-1998) + 40,483 where x = the year of the desired projection (must be after 1998) 40,483 = estimated number of BRW cows in = coefficient which describes yearly growth rate. Table 6 shows the estimated number of BRW cows in the years 2000, 2010 and 2020 using the equation shown above. Table 6: Projected BRW Cow Numbers Based on Regression Equation Year # cows Growth from ,578 3% ,051 16% ,524 30% Using the regression equation, the projected number of cows in the BRW in 2020 (52,524) is lower than the currently permitted number of cows in the watershed (67,074). Using the larger of the projected and current permitted number of cows, 67,074 total cows are used in the project s considerations for 20 years of future growth. Projections of Row Crop Production in the Bosque River Watershed Approximately 16 percent of the land in the BRW is used for row crops (McFarland and Hauck, 1998). Runoff from crop fields can contain excess fertilizer, which can lead to nutrient over-enrichment. An examination of land use percentages from 1977 and 1996 shows very little change in amount of BRW cropland during the 19 year period. The 1977 land use data were obtained from the USDA Computer-Based Mapping System (CBMS) digital database of aerial photography of Bosque, Coryell, Hamilton and McLennan counties. The 1996 data were developed by USDA Natural Resources Conservation Service from 1996 Landsat TM scenes. The original land use designation combined both row crops and non-row crops, such as improved pasture, into one category termed cropland. In order to identify just the row crops, differentiation in cropland type was assigned based on location in the watershed. Because of soil types and general land use practices, any cropland acres above Hico were considered to be improved pasture, while those below Hico were considered to be row crops. 22

23 Future Growth Projections for the Lake Waco/Bosque River Watershed Future Growth Projections Table 7 presents the number of acres used for row crops in each of the major subwatersheds of the BRW, the percentage of total acreage in the subwatershed used as row crops, and the percentage change from 1977 to The BRAC subcommittee reviewed the data and deemed the amount of change to not be of sufficient magnitude to warrant additional future growth allocation. Table 7: Changes in BRW Row Crop Acres, 1977 to 1996 Row Crop Acres Part of Watershed Used for Row Crops 1977a 1996b Change Entire BRW 168, , % 16.1% <1% North Bosque 44,562 61,582 6% 8% 38% Hog Creek 23,737 20,840 41% 36% -12% Middle Bosque 61,348 53,496 48% 42% -13% South Bosque 29,720 27,539 51% 47% -7% Other 9,007 7,216 30% 23% -20% a. CBMS landuse data b. Landsat TM imagery Projections of Unallocated Municipal/Industrial Contributions to the Bosque River Watershed In order to account for future municipal or industrial growth that generates wastes not treated by existing WWTPs, the BRAC recommended allocating some pollutant loading for unknown industries moving into the watershed. As an initial estimate, approximately 10 percent of the currently permitted WWTP effluent discharge limit is allocated for future municipal and industrial growth. Using the total from Table 2 yields an additional 0.6 MGD of effluent to the river system. 23

24 Future Growth Projections for the Lake Waco/Bosque River Watershed Summary To estimate the future growth of potential pollution sources for the USDA Initiative, areas of potential growth with respect to phosphorus loading in the watershed have been examined. These areas include urban population growth, wastewater treatment plant effluent discharge, numbers of dairy cows, acres of land used for row crop production, and potential municipal and industrial contributions. Projected increases in each area were estimated for an approximate 20-year horizon to the year 2020, with intermediate projections for the year Regulatory limits exist for wastewater treatment plant effluent and dairy cow numbers. Projected growth in neither area equals the current regulatory limits. Because the potential exists for all WWTPs and dairies to increase to their authorized maximum, the sum of the effluent limits for WWTPs and the maximum number of dairy cattle will be used as the projected levels in the year Growth in acres used for row crop production is not anticipated to increase significantly above its current level of 16 percent of the total watershed acres. Currently all effluent from industrial producers in BRW is handled by local WWTPs. In order to allow for additional future growth in the watershed, notably in the municipal and industrial areas, an allotment of 10 percent of the current WWTP effluent is projected. This adds an estimated 0.6 million gallons of effluent per day to the system. Future contributions to be used in the modeling efforts and other analyses for the USDA Lake Waco/Bosque River Initiative project are shown in Table 8. Table 8: Summary of Future Growth Projections for the BRW Component 2020 Projection Change from Current Conditions or Permit Limits Total urban population 84,190 people +19,777 (31%) Total WWTP effluent MGD None Total number of dairy cows 67,074 cows None Total acres of row crops 170,673 acres None Other point source growth 0.6 MGD effluent +0.6 MGD 24

25 References McFarland, Anne and Larry Hauck Stream Water Quality in the Bosque River Watershed, October 1, 1997 through March 15, Report No. PR9705. Stephenville TX: Texas Institute for Applied Environmental Research, Tarleton State University. Ramos, M. and Robert Plocheck eds Texas Almanac Dallas, TX: The Dallas Morning News, Inc. Texas Natural Resource Conservation Commission (TNRCC) State of Texas 1999 Clean Water Section 303(d) List (Draft). Austin, TX: TNRCC State of Texas 1998 Clean Water Section 303(d) List. Austin, TX: TNRCC State of Texas 1996 Clean Water Section 303(d) List. Austin, TX: TNRCC. Texas Water Development Board (TWDB) Water for Texas - Today and Tomorrow, A 1996 Consensus-Based Update to the Texas Water Plan. Vol 3, Water Use Planning Data Appendix. Austin, TX: TWDB. USDA. The Market Administrator s Report: The Texas Marketing Area, New Mexico -West Texas Marketing Area. Monthly editions from January 1985 through December Carrollton, TX: USDA. 25

26 Future Growth Projections for the Lake Waco/Bosque River Watershed 26

27 APPENDIX A City of Waco Population and WWTP Projections for the BRW Area Population Projections Representatives from the City of Waco provided the following population figures for the portion of Waco located within the Bosque River watershed. These projections were prepared for them by The Texas A&M University: Year Population 33,200 44,200 These figures represent an increase of 11,000 people over the 17 year period, or 647 people annually, assuming growth will take place in equal amounts each year. Population projections for 2000, 2010, and 2020 were calculated using equal annual increases in population, as shown below. Year Population 33,200 34,494 40,965 44,200 47,435 Wastewater Treatment Plant Projections Three subdivisions are scheduled to be developed within the City of Waco s jurisdiction. Residences currently located in those areas use onsite septic systems. Permits that would allow package wastewater treatment facilities to discharge into the BRW have been obtained for each of the three residential developments. If the package treatments are installed, they are not anticipated to be used past the year The residential developments will be connected to Waco s wastewater collection system which discharges into the Brazos River watershed. Table A-1 shows combined daily average flow limits, plus the daily average flow and the predicted flow for WWTP discharge from the City of Waco into the BRW. 27

28 Future Growth Projections for the Lake Waco/Bosque River Watershed Table A-1: WWTP Effluent Discharge Projections for the City of Waco Located in the BRW City Daily Avg Flow Limit (MGD) Daily Avg Flow (MGD) Estimated Flow in 2020 (MGD) Percentage Increase 2020 Flow as Percent of Limit Waco % 0.0% 28

29 APPENDIX B WWTP Effluent Projection Calculations WWTP effluent projection calculations are based on population growth in the area served by the WWTP. (a) POPULATION GROWTH RATE: City population estimates for 2000, 2010 and 2020 were obtained from the TWDB web-site or from city representatives. The growth rates in city population were calculated by subtracting one decade s population from the next decade s population and dividing by the first decade s population (Table B- 1). Table B-1: Population Growth Rate Calculations Population Growth City Clifton 3,557 3,961 4, % 7.8% Crawford % -3.2% Hico 1,380 1,400 1, % 1.2% Iredell % 14.3% McGregor 5,228 5,670 5, % 3.1% Meridian 1,504 1,603 1, % 11.7% Stephenville 16,060 18,638 21, % 13.2% Valley Mills 1,090 1,107 1, % 1.0% Waco 34,494 40,965 47, % 15.8% TOTAL 64,413 74,505 84, % 13.0% (b) DAILY AVERAGE DISCHARGE RATE: Monthly averages of daily effluent discharge for each WWTP, obtained from self-reporting data submitted to TNRCC, were averaged across the period of January 1997 through December Because of weather and usage variations, it was felt that two years of data would likely yield a more representative average daily discharge than a single year is the last year 29

30 Future Growth Projections for the Lake Waco/Bosque River Watershed for which complete data are available, so the average daily flows were designated as 1998 averages. Average discharges are shown in Table B-2. (c) DISCHARGE PROJECTIONS: The discharge rate for each WWTP was multiplied by the decade s population growth rate for that city to yield the discharge projection. Two-tenths of the growth rate for was used for the two year period from Projections are shown in Table B-2. Table B-2: WWTP Discharge Projections City 1998 Avg Dischg 2000 Dischg 2010 Dischg 2020 Dischg Clifton Crawford Hico Iredell McGregor Meridiana Stephenville Valley Mills Waco TOTAL a. Representatives from Meridian projected increases larger than those due to population increase alone. That increase and the resulting different totals are reflected in Table 2. Cranfills Gap is a small community located on a tributary to Meridian Creek, which flows to the North Bosque River. Although the town does not currently have a WWTP and TNRCC has not received a permit application for the proposed WWTP, TIAER researchers have been informed that funding has been secured for a Cranfills Gap WWTP. A rough estimate of future wastewater discharges in Cranfills Gap, based on the current number of water meters and the TWDB projected growth rate for nonurban areas of Bosque County, yielded less than a one percent change in total discharge of effluent in In addition, the WWTP would discharge near the headwaters of Meridian Creek, over twelve miles from the North Bosque River, which substantially reduces impacts to the North Bosque River. Therefore, the potential WWTP for Cranfills Gap was not included in effluent discharge projections. 30

31 APPENDIX C Additional Details of Determining Cow Numbers TNRCC wastewater discharge permits for dairies designate a maximum allowable number of cows. Some permits designate milking head; other permits designate total head, while others simply state a number of head. This discrepancy can result in a notable difference in total number of cows. Cows lactate an average of 305 days a year, and are dry the remaining 60 days. Multiplying the number of milking head by 20 percent approximates average number of dry cows. TNRCC permits for all BRW dairies were examined for wording. Cow numbers on permits designating milking cows were increased by 20 percent to accommodate dry cows. Cow numbers for permits designating either total head, head, or cows remained as stated for calculation purposes. This raised the permitted total for the BRW from 67,217 to 70,008 cows. Note: Dairies with fewer than 200 cows (or 250 if they were in operation prior to 1995) are not required to have a TNRCC wastewater discharge permit and, unless otherwise designated, were counted as being "permitted" to have 199 cows (or 249), which is the regulatory allowable number. A number of dairies are located on the boundary of the Bosque River watershed, with acreage in both the Bosque and adjacent watersheds. Whatever proportion of the dairy s waste application fields are located in the BRW is also applied to the cows. For example, if 60 percent of a dairy s waste application fields are located in the BRW, then 60 percent of the cows are counted as BRW cows. This procedure was applied to dairies whose facilities are located in the BRW, with some acreage in adjacent watersheds, as well as dairies whose facilities are located in other watersheds, but have some acreage in the BRW. Dairies that haul manure off their property also are proportioned in this same manner. This adjustment reduced the permitted total for the BRW in Erath and Hamilton counties from 70,008 to 64,734 cows. The number of actual cows, as opposed to a maximum allowable or permitted number of cows, was estimated from TNRCC inspection reports for the years 1997 through 1999 for 67 of the watershed s 107 dairies, including the two dairies outside Erath and Hamilton counties. The TNRCC inspection numbers were revised for dairies whose waste application fields lay only partially within the BRW, just as the permitted numbers were adjusted. Thirty-six dairies, plus four out-of-business dairies, had no TNRCC inspection report on file between 1997 and The number of actual cows on the uninspected dairies was estimated by multiplying the number of permitted cows on those dairies by the ratio of actual-to-permitted cows on the inspected dairies. This ratio was calculated by dividing the actual TNRCC inspection total by the adjusted permitted total for the watershed, excluding the two dairies out- 31

32 Future Growth Projections for the Lake Waco/Bosque River Watershed side Erath and Hamilton counties. The ratio, 0.642, and the other figures are shown in Table C-1, which is an expanded version of Table 4. Dairies included on TNRCC s most current list of permitted dairies, but which are currently out of business, were not used in calculating the permitted to actual cow ratio nor in the regression analyses. However, because those dairies could resume operations, their permitted numbers of cows were included in the total number of permitted cows in the watershed. As noted in the text, a review of TNRCC permit files showed that between January to August 1999, an additional 1,290 cows were permitted in the BRW. These were added to the total permitted number at the request of the BRAC, in order to more accurately estimate the cow population in the watershed. Table C-1: Figures Used in Estimating the Number of BRW Cows in 1998 Type of Dairy # of Dairies Maximum Allowable Permitted Converted to Total Adjusted for Basin Boundaries Estimated Actual Number % of Actual/ Maximum Allowable Inspected Dairies 65 42,062 44,155 42,527 27, Uninspected Dairies 36 22,660 23,358 19,712 12,649 Out-of-Business Permitted Dairies Total in Erath and Hamilton Outside Erath and Hamilton 4 2,495 2,495 2, ,217 70,008 64,734 39, ,050 1,050 1, Permitted in ,290 1,290 1,290 0 TOTAL ,557 72,348 67,074 40,483 32