FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan 6 WATER RESOURCES SETTING 6.1 Climate and Precipitation Figure 6‐1 Average Monthly Rainfall Distribution (Lodi Station) The climate in San Joaquin County is characterized by long, dry summers with an average growing season of 292 days. 4 Cold and rainy conditions occur in November and last through April with almost 90 percent of the annual 3 precipitation falling in these months. The average annual rainfall is about sixteen inches per year and varies due to 2 orographic effects across the Coastal Foothills in the west to Rainfall Rainfall (in) the Sierra Nevada Foothills in the east. Temperatures can 1 exceed 110 degrees in the summer and may also fall to the low 20’s in extreme cold weather events.49 Figure 6‐1 and 0 N B R R N L E P U UG Figure 6‐2 depict the annual and monthly variation in OCT NOV DEC JA F MA A MAY JU J A SEP precipitation. Month (Water Year Calendar) Figure 6‐2 Total Annual Rainfall 1941‐2012 (Stockton Fire Station) 49 San Joaquin County General Plan 2010 Chapter 6 6-1 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan 6.2 Urban Land and Water Use Accommodating planned growth in San Joaquin County is a huge challenge for land use entities throughout the Regional Planning Area. The current population of San Joaquin is expected to increase by approximately 48 percent by 2030 from nearly 690,000 to over 1.0 million. Land use in the Eastern San Joaquin Regional Planning Area is summarized based on GIS mapped urban areas, the latest DWR land use survey completed in 1996, and the projected urban spheres of influence as reported in adopted or draft general planning documents. For the purposes of this IRWMP, the “current” planning level is assumed to be 2010 for urban and water use while “future” conditions assume a 2035 planning horizon. The IRMWP assumes that urban growth will occur as either infill or entirely within spheres of influence (SOI) delineated in the latest general plan revisions. To account for the loss of agricultural production, it is assumed that existing agricultural irrigation within the SOI will be entirely replaced with urban uses by 2035. Figure 6‐3 and Figure 6‐4 depict the 2010 and projected 2035 urban footprints. Water use within the urban areas of the Regional Planning Area is summarized based on current Urban Water Management Plans, water production data obtained from water service providers, or other general planning documents. Table 6‐1 summarizes the current and projected water demands, urban footprint acreage, and water use per acre. The net increase in annual urban demand from 2010 to 2035 is estimated to be approximately 72,000 acre‐feet. Urban areas are projected to expand and population is projected to grow, but overall use per capita is projected to decline. Several agencies are aggressively implementing many of the best management practices and demand management measures (BMPs/DMMs) recommended by the California Urban Water Conservation Council. In many cases, the 2035 demands reflect reductions attributed to the implementation of current and future conservation programs. Changes in population density, infill development, subsequent general plan revisions, and increased water conservation may affect the accuracy of the projected water demand. 6.3 Agricultural Land and Water Use Irrigation throughout the Regional Planning Area are mostly un‐metered, so water use estimates are based largely on cropping patterns and the associated applied water demand. The DWR Division of Planning and Local Assistance collects unit crop and applied water use estimates throughout the State for the preparation of DWR Bulletin 160, the California Water Plan Update. The following sections describe the method, crop inventory, and applied water demand for the Regional Planning Area. Chapter 6 6-2 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan Table 6‐1 Current and Future Urban Water Demands 2010 2035 Urban City Urban Unit Use SOI Unit Use Use Limits Use (af/yr) (acres) (af/yr) (af/yr) (acres) (af/yr) Urban Areas Escalon 2,705 1,501 1.80 4,742 2,144 2.21 Lathrop 19,043 12,671 1.50 31,647 15,685 2.02 Lodi 21,109 8,926 2.36 25,539 10,653 2.40 Manteca 29,588 12,873 2.30 43,076 20,351 2.12 Ripon 8,235 3,524 2.34 17,601 7,108 2.48 Stockton 73,886 41,763 1.77 113,895 72,714 1.57 Urban Total 154,566 81,257 1.90 236,500 128,656 1.84 Change +53% +58% ‐3% Note: Includes agricultural uses within city limits or sphere of influence 6.3.1 Agricultural Land Use DWR performs detailed land use surveys Statewide at unspecified intervals. For San Joaquin County, land use surveys were performed in 1976, 1982, 1988, and 1996. The IRWMP utilizes the latest land use survey performed in 1996 and assumes that changes in land use since 1996 are accurate enough to support planning level estimates of agricultural water use. Table 6‐2 summarizes the historic land use summaries and illustrates trends of increasing vineyards, orchards, and urban areas, with decreasing amounts of land for pasture, miscellaneous truck and field crops, and farmstead crops. To account for changes in urban land use since 1996 to current conditions and beyond, the 2010 “current” and 2035 “future” urban foot prints were spatially overlaid upon the 1996 land use survey. All agricultural lands within the urban foot prints are considered to be entirely converted to urban uses. A summary of agricultural and urban land uses 2010 and 2035 is presented in Table 6‐3. Figure 6‐3 and Figure 6‐4 depict the spatial distribution of land use for both the 2010 and 2035 conditions. Chapter 6 6-3 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan Table 6‐2 San Joaquin County Land Use Summary (acres) Land Use 1976 1982 1988 1996 2005 2030 Urban 59,221 57,557 74,186 86,550 120,860 180,160 Orchard 87,294 96,322 102,895 107,784 103,720 95,650 Pasture, Truck, Field, & Farmstead 458,248 439,497 454,778 393,297 370,249 328,760 Rice 7,918 7,865 6,141 5,991 5,990 5,990 Vineyards 60,921 65,646 63,860 76,975 76,070 72,150 Native & Riparian Vegetation 213,922 202,073 201,133 218,056 212,510 208,072 Water Surface 17,576 27,128 22,755 22,621 21,550 20,170 TOTAL 905,100 896,088 925,748 911,273 910,950 910,950 Source: DWR Land Use Surveys ‐ San Joaquin County 1996 Note: San Joaquin County comprises 901,760 acres. The difference between the land use total and the area of the County is attributed to double‐cropping. Chapter 6 6-4 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan Figure 6‐3 2010 City Limits and Land Use Map Chapter 6 6-5 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan Figure 6‐4 2035 Urban Spheres of Influence and Land Use Map Chapter 6 6-6 Water Resources Setting FINAL – 6/05/2014 – R21 2014 Eastern San Joaquin Integrated Regional Water Management Plan 6.3.2 Land Use Summary A summary of existing (2010 level of development) and projected (2035 level of development) is presented in Table 6‐3. Table 6‐3 Summary of Existing and Future Land Use 2010 Area (acres) 2035 Area (acres) Within IRWM Area Outside IRMW Area Within IRWM Area Outside IRMW Area Total Total M&I Agricultural M&I Agricultural M&I Agricultural M&I Agricultural Urban Areas Escalon 1,237 264 ‐ ‐ 1,501 1,306 838 ‐ ‐ 2,144 Lathrop 5,817 1,117 1,366 4,371 12,671 7,122 2,817 1,375 4,371 15,685 Lodi 7,470 1,456 ‐ ‐ 8,926 8,402 2,251 ‐ ‐ 10,653 Manteca 9,052 3,821 ‐ ‐ 12,873 11,665 8,686 ‐ ‐ 20,351 Ripon 2,917 607 ‐ ‐ 3,524 3,488 3,620 ‐ ‐ 7,108 Stockton 35,918 4,924 921 ‐ 41,763 51,893 19,278 1,098 445 72,714 Tracy ‐ ‐ 12,032 1,846 13,878 ‐ ‐ 23,607 10,321 33,928 Unincorporated Urban Areas 25,623 ‐ 8,131 ‐ 33,754 12,958 ‐ 4,459 ‐ 17,417 Urban Total 88,034 22,450 110,484 96,834 30,539 127,373 Agricultural Areas Central Delta Water Agency ‐ 38,907 38,907 35,227 35,227 Central San Joaquin Water Conservation District 55,185 55,185 50,521 50,521 North San Joaquin Water Conservation District 66,385 66,385 66,145 66,145 Oakdale Irrigation District 5,719 5,719 5,719 5,719 South Delta Water Agency 12,996 12,996 11,504 11,504 South San Joaquin Irrigation District 46,159 46,159 37,715 37,715 Stockton East Water District 59,788 59,788 56,447 56,447 Woodbridge Irrigation District 26,238 26,238 25,105 25,105 Other Agriculture 41,370 149,603 190,973 39,065 140,683 179,748 Ag Total 364,937 155,820 520,757 364,937 155,820 520,757 Remaining Acreage (Native Veg, Water, etc.) 168,468 113,741 282,209 159,668 105,652 265,320 Acreage Total 621,439 292,011 913,450 621,439 292,011 913,450 6.3.3 Agricultural Water Use Agricultural water use is based on various crop Evapotranspiration (ET) and efficiency data collected by DWR.