Groundwater budgets for Detrital, Hualapai, and Sacramento Valleys, Mohave County, Arizona, 2007-08

Abstract

The United States Geological Survey, in cooperation with the Arizona Department of Water Resources, initiated an investigation of the hydrogeology and water resources of Detrital, Hualapai, and Sacramento Valleys in northwestern Arizona in 2005, and this report is part of that investigation. Water budgets were developed for Detrital, Hualapai, and Sacramento Valleys to provide a generalized understanding of the groundwater systems in this rural area that has shown some evidence of human-induced water-level declines. The valleys are within the Basin and Range physiographic province and consist of thick sequences of permeable alluvial sediment deposited into basins bounded by relatively less permeable igneous and metamorphic rocks. Long-term natural recharge rates (1940-2008) for the alluvial aquifers were estimated to be 1,400 acre-feet per year (acre-ft/yr) for Detrital Valley, 5,700 acre-ft/yr for Hualapai Valley, and 6,000 acre-ft/yr for Sacramento Valley. Natural discharge rates were assumed to be equal to natural recharge rates, on the basis of the assumption that all groundwater withdrawals to date have obtained water from groundwater storage. Groundwater withdrawals (2007-08) for the alluvial aquifers were less than 300 acre-ft/yr for Detrital Valley, about 9,800 acre-ft/yr for Hualapai Valley, and about 4,500 acre-ft/yr for Sacramento Valley. Incidental recharge from leaking water-supply pipes, septic systems, and wastewater-treatment plants accounted for about 35 percent of total recharge (2007-08) across the study area. Natural recharge and discharge values in this study were 24-50 percent higher than values in most previously published studies. Water budgets present a spatially and temporally "lumped" view of water resources and incorporate many sources of uncertainty in this study area where only limited data presently are available. alluvial fill varies by location and depth, but it generally is greatest at the basin margins and along stream channels and is smallest in basin centers. Metamorphic and volcanic rock (hereafter, bedrock) define the margins and floors of the alluvial basins. The margins are topographically high water resource data, accessed June 1, 2009, at http://gisweb. azwater.gov/waterresourcedata/ .

Preliminary groundwater flow model of the basin-fill aquifers in Detrital, Hualapai, and Sacramento Valleys, Mohave County, northwestern Arizona

“…Subsequent spatial analysis by Garner and Truini (2011) determined that bank storage and soil moisture were the most likely sources of water for this vegetation, and the amount of groundwater discharge through evapotranspiration from the alluvial basins in the study area is considered negligible. …”

“…Annual groundwater budgets quantifying volumes of water flowing into and out of Detrital, Hualapai, and Sacramento Valley alluvial aquifers were presented in Garner and Truini (2011). These water budgets were calculated as average basin-wide conditions for 2007-08 except for natural aquifer recharge from precipitation, which was calculated as a long-term average for 1940-2008.…”

“…Predevelopment water budgets, although not expressly presented by Garner and Truini (2011), can be inferred by omitting groundwater withdrawals and incidental recharge (table 1). Human activity was assumed to have not affected natural recharge or discharge rates as of 2007-08, and natural-recharge rates were calculated as long-term averages in the study.…”

“…Natural aquifer recharge in Detrital Valley from precipitation was the lowest Table 1. Predevelopment groundwater-budget values for Detrital, Hualapai, and Sacramento Valleys from Garner and Truini (2011).…”

“…These three arid basins contain no perennial surface-water features, and so residents and industry rely on groundwater to meet water needs. Recent and projected population increases for the study area, along with proposed solar-energy-production facilities Results from the hydrogeologic studies in these basins include an investigation of groundwater occurrence and movement and groundwater-level changes (Anning and others, 2007), an estimate of groundwater budgets (Garner and Truini, 2011), an updated geologic map of the study area (Beard and others, 2011), and a hydrogeologic framework and estimates of groundwater in storage (Truini and others, 2013). These studies, along with the preliminary groundwater-flow model presented in this report, provide information and tools for those tasked with managing water resources in the area to assist in better understanding the existing groundwater system and to help plan for potential changes in the groundwater system from future changes in water use, climate effects, and other stresses.…”