1. E. Leigh, M.Barroso, and G. Fippshttp://idea.tamu.edu College Station, TX 77843-2117 E. Leigh, M.Barroso, and G. Fipps http://idea.tamu.edu College Station, TX 77843-2117http://idea.tamu.edu Expansion of Urban Area Rio Grande River Basin, 1996 - 2006 Rio Grande River Basin, 1996 - 2006 Department of Biological and Agricultural Engineering Texas A & M University System About this Map Series The border region of Texas is experiencing rapid urban growth which is expected to have a continuing and increasing impact on the irrigation districts of the region. We analyzed the expansion of the urban area during the ten year period from 1996 to 2006 in portions of the Rio Grande Basin, which include: El Paso, Maverick, Cameron, Hidalgo and Willacy Counties. The report includes maps of these five counties showing both of the urban expansion and the service areas of 30 irrigation districts. Cameron, Hidalgo, and El Paso County maps are shown in figures 1, 2, and 3, respectively. Individual maps of the districts were also produced and have been distributed to each district. These maps can be seen at http://idea.tamu.edu.http://idea.tamu.edu Definition of Urban Area and Irrigation District For this map series, “urban area” is loosely defined as a continuous developed and/or developing area that is no longer in agricultural use. We included all residential communities and subdivisions (with or without homes) that are clearly identifiable from aerial photographs. We also included properties with more than one dwelling or other structure on a single piece of property. Single dwellings on large properties outside the city limits were excluded. Here, the term “irrigation district” refers to all irrigation, water control, water improvement, conservation, reclamation, and municipal utility districts that deliver agricultural irrigation water and hold Class A Agricultural Water Rights or a similar allocation. Summary of Analysis For this analysis, we used our estimate of the size of the service areas of the water districts. Urban area estimates have about a 10% margin of error. No legal descriptions of properties or survey data were used in the development of this map series. This project is solely intended to be an estimate of the urban growth in these particular counties and to illustrate possible trends affecting agriculture and irrigation district operations. Table 1. Urban Area within Counties in 1996 and 2006. Counties Total Acreage Urban Area 1996Urban Area 2006Increase Acreage % Cameron613,03666,18981,63523 El Paso656,492208,180234,15512 Hidalgo1,012,982118,466160,09535 Maverick826,9159,81612,01922 Willacy393,8193,0843,50914 Table 2 lists our estimate of the total urban area within each district in terms of acres and in percentage increase from 1996 and 2006. HCID2 has the largest number of urban acres, while the largest increase in urban area as a percentage of the district was in HCID16, HCID18 and HCID19. On the other hand, there was no increase in VMUD2 and Valley Acres. Based on water rights (, the districts vary greatly in size. In the Lower Rio Grande Basin, the smallest active district has 1,120 ac-ft of Class A Water Right, while the largest district has 177,151 ac-ft. Actual water allocations in any given year depend on the amount of water stored in Amistad and Falcon Reservoirs. Table 2. Urban Acreage within Irrigation Districts in 1996 and 2006. Urban Area 1996 Urban Expansion through 2006Percent Increase DistrictAcreage Adams Garden5321,380160 % Bayview24120392 % Brownsville8,7249,91514 % CCID1626041560 % CCID28,38410,92530 % CCID64,4397,94879 % CCWID1013522466 % Delta Lake1,1271,84163 % Donna4,3577,31068 % El Paso32,96735,4438 % Engelman144331130 % Harlingen14,66216,95516 % HCCID916,72122,71636 % HCID122,63325,32712 % HCID13117469302 % HCID16831,0051109 % HCID1901,908– HCWCID18153001924 % HCID233,00639,10719 % HCID51,1421,42425 % HCID65,6779,59569 % HCMUD11,0161,81178 % HCWID36,6186,9365 % La Feria2,6263,80945 % Maverick9,79411,97222 % Santa Cruz2,8893,71529 % Santa Maria24236551 % United15,33617,79416 % Valley Acres162 0 % VMUD21,142 0 % El Paso County Water Improvement District No.1 is allocated water according to the Rio Grande Compact. The District receives 388,000 ac-ft ( “ full allocation ” ) or 43% of the available water supply in Elephant Butt and Caballo Reservoirs, whichever is less. Hudspeth County Conservation & Reclamation District No.1 has Texas Class B water rights, and therefore is authorized to use water available downstream of El Paso. Portions of the Rio Grande Basin of Texas are undergoing rapid urban growth which is resulting in “ fragmentation ” of many irrigation districts. Table 1 lists our estimates of the expansion of total urban area from 1996 to 2006 by county. The highest increase in both area and as a percentage of total area was in Hidalgo County. Figure 1 Figure 2 Figure 3