Lower Rio Grande Valley Groundwater Transport Model Page: PAGE 34
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MONTGOMERY Conceptual Model Report:
wr O TG M R Lower Rio Grande Valley
& ASSOCIATES Groundwater Transport Model
water use surveys collect estimates for six sectors: municipal, irrigation,
manufacturing, steam-electric generation, livestock, and mining. Total annual
groundwater pumping estimates for each county in the Lower Rio Grande Valley
are summarized in Table 4.7.1. The majority of groundwater pumping in the
valley has occurred in Hidalgo County and, to a lesser degree, Cameron County
(Figure 4.7.1). Although pumping varies from year to year, groundwater
pumping in the valley has generally increased since the late-1980s. Total
groundwater pumping was approximately 22,000 AF/yr in 1984 which increased
to approximately 32,000 AF/yr in 2013. According to the water use surveys, total
annual pumping was at a peak rate of approximately 53,000 AF/yr in 2009;
however, estimates for Cameron County for that year appear to be anomalously
large. The large amount of year-to-year variation in the amount of groundwater
pumping is likely a result of occasional drought conditions, which reduce surface
water supplies and require existing users to switch to groundwater sources
(Chowdhury and Mace, 2007).
Estimated annual groundwater pumping in the valley by water use sector from
1984 to 2013 is shown on Figure 4.7.2. Groundwater withdrawals during this
time period occurred predominantly for irrigation and municipal uses during most
years until 2002. After 2002, estimates irrigation pumping decreased
substantially and municipal pumping increased, according to TWDB water use
surveys. This change in pumping trends might be due to changing water demands
or inaccurate information in the water use surveys.
Domestic pumping estimates are not included in the TWDB water use surveys.
For historical domestic pumping, an estimated pumping rate per domestic well
was used based on an assumption used for the 2016 Region M Water Plan by
Black & Veatch (2015). The water plan assumed that each domestic well yielded
0.4 AF/yr based on 140 gallons per capita per day and 2.5 people per household,
and these wells were assumed to be reported 50 percent of the time. The number
of reported domestic wells located within the valley was determined using records
obtained from the TWDB groundwater database. To account for the assumption
that the database includes only 50 percent of the domestic wells that are actually
present in the valley, the assumed pumping rate per well was doubled to 0.8 AF/yr
and applied to each reported domestic well. Estimated annual domestic pumping
is relatively small in the valley (Table 4.7.1 and Figure 4.7.2).
Locations of groundwater production wells in the Lower Rio Grande Valley were
obtained from the TWDB groundwater database (TWDB, 2015). In addition to
well locations, the groundwater database included information for well
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Montgomery & Associates. Lower Rio Grande Valley Groundwater Transport Model, report, June 30, 2017; Austin, Texas. (https://texashistory.unt.edu/ark:/67531/metapth1114946/m1/50/: accessed July 17, 2024), University of North Texas Libraries, The Portal to Texas History, https://texashistory.unt.edu.; crediting UNT Libraries Government Documents Department.