Report Proposal Status:
Original 2 pager First Update: 00/00/00 --changes marked in red print
Second Update: 00/00/00 --changes marked in green print
Principal Aquifer:
Aquifer Name(s): BARA - Basin and Range / California Aquifers; Rio Grande, Colorado River and Great Basins (MRB 6); California River Basins (MRB 8)
Lead Contact: Sue Thiros
Proposed Report Title:
Impact of flow-system alteration on ground-water quality in the arid to semiarid western United States
Scope:
Components: NAWQA Major Aquifer Studies, and selected Source Water Assessment and Flow path Studies; constituents: VOCs, pesticides, nitrate, tritium, age-dates
Study Units: NVBR, GRSL, CAZB, SANJ, SACR, & SANA-SOCA
Time Period: Cycle I and II
Land Use(s): urban, agriculture
Inter-Regional Principal Aquifer Proposal? Yes/No: Explain: Yes
Constituents:
Expected Authors:
Lead: Hamlin, Dawson
Contributing: Thiros, Brown, Rosen, Burow, Belitz
Objectives:
Define and quantify anthropogenic alteration of ground-water flow systems used for public supply in the 6 BRCA study units.
Characterize flow systems in each basin, locations of recharge and discharge (natural and anthropogenic), configuration of ground-water flow directions (convergent (dispersed recharge, concentrated discharge) divergent (concentrated recharge, dispersed recharge), parallel), and changes caused by human alterations to ground-water flow systems.
Compare the occurrence of target constituents in MAS wells across the region with the alteration factors (e.g. amount of pumping, applied irrigation, engineered recharge, source and amount of imported water) and to flow system configurations to understand what water-quality factors may be controlled by human alterations to ground-water flow systems.
Stage project efforts and review 3 to 4 months into the study. Do some exploratory data analysis on part of the data set, over a spectrum of conditions, to see if there is enough data to do what is proposed and if the results are satisfactory. Transfer knowledge to and from the Ground-Water Trends group.
Data Interpretation Approach and Feasibility:
Number of Sites/Components (e.g., nutrients, pesticides):
NAWQA Major Aquifer Studies, and selected Source Water Assessment Studies, Flow path Studies, and other wells that can provide data useful at a regional scale; Constituents: VOCs, pesticides, nitrate, tritium, age-dates, other constituents (stable isotopes, major ions, trace elements) that can show a difference in “anthropogenic” water compared to “natural” water.
Methods:
Need to define and quantify “alteration” of flow system, such as amount of imported water recharged, amount of artificial/engineered recharge to ground water, amount of irrigation return, amount of ground water pumped, precipitation amounts, length of time system has been altered, changes in flow directions, increase in flow rates due to alteration.
Analysis of distribution of analytes along ground-water flow paths, correlation tests of water-quality indicators with alteration factors, depth to water, well depths, distance from recharge, and other secondary variables; comparisons of water quality by categorical variables, which may include confined/unconfined, shallow/deep, proximal/distal, general flow system configuration (convergent, divergent, vertically dominated, horizontally dominated), land use type, population density, crop acreage, irrigation/public supply water usage, presence absence of tritium (and other analytes) and pesticide use.
Compare basins by sources of anthropogenic water (surface water from within basin, imported from nearby basins, imported Colorado River water, treated effluent, etc).
Data Availability and Processing:
NAWQA data for analyte concentrations and well data are readily available (NAWQA data warehouse). Acquisition and processing of ancillary data sets that are consistent across study units will take more time, and the most useful sources and methods of analysis will need to be identified.
Known sources of data:
Precipitation data – PRIZM data
Water Use data – Estimated water-use for 1990, 1995, and 2000 by county or watershed available online http://water.usgs.gov/wateruse/, (2000 data should be published online soon), includes ground water and surface water withdrawals by use category (public supply, irrigation, etc.), acres irrigated, and other potentially useful data; needs to be downloaded and processed in each basin.
Land Use data – MRCL (1990s) data and GIRAS (1970s) data available from NAWQA
Amount of imported water to basin, amount of imported water recharged, amount of artificial/engineered recharge to ground water, amount of irrigation return, potentiometric-surface maps, and regional ground-water levels and flow directions, history of water and land use – sources unknown for all areas and will be gathered during the first year of the study.
Staff Availability: Staff is available beginning in FY05 from the study units that are part of the Principal Aquifer Team.
Complexity: Medium to high. There is a need to define “alteration” of flow systems and to determine how best to quantify it using readily available data that are consistent across the study units.
Risks/Contingencies: This report may take more time than other proposed reports to complete ancillary data acquisition and data analyses. The plan is to collect and assess ancillary data in FY05; analyze and interpret the data and write most of the draft report in FY06; and review and publish the report in FY07. The plans for FY06 and 07 are based on data being available and collected in FY05. If the FY05 work is not successful or requires more effort to gather the necessary information, then the study will need to be planned accordingly.
Other Program Contacts: Western NAWQA study units, VOC and Pesticide National Synthesis Teams, Transport of Anthropogenic and Natural Contaminants and Agricultural Chemicals Topical Teams, other Principal Aquifer Teams, proposed salinity report team, other USGS projects and outside agencies that can provide water use, land use, and other ancillary data.
Expected Outcome:
The degree of human alteration of hydrologic systems is an important explanatory factor for ground-water quality. In the first cycle of NAWQA, studies were designed to test the degree to which land use was a primary explanatory factor for water quality. We expect the degree of flow system alteration to be equally as important.
Highly developed and managed ground-water systems move more water and anthropogenic compounds into ground-water, usually leading to an increase in compounds in ground water. However, the impact on ground-water quality depends on the quality of introduced water (for example, introduction of pesticides to ground water by recharge of irrigation water, or conversely, the dilution of anthropogenic compounds introduced at land surface by clean impounded mountain storm water recharged to ground water), and the degree of confinement of the aquifer system (well-confined systems are insulated from compounds introduced at land surface).
Why is this topic important to report on?
This report addresses western issues of increasing use of ground water in arid to semiarid regions for water supply and the effects of increased usage/pumping and the use of imported water and engineered recharge on ground-water quality.
Why does this topic need to be addressed now?
The expansion of agricultural and urban areas and increases in ground-water use are increasing the amount of alteration of natural-flow systems (use of aquifer storage-recovery, engineered recharge, inter-basin transfers of water, limitations on surface water use). Many agencies are currently developing ground-water management plans, making decisions on how to govern the expansion of urban areas. A better understanding of the effects of flow alteration can help water managers maintain ground-water quality along with increasing development.
Why is it appropriate for this topic to be addressed by the USGS? NAWQA? This Regional Team?
The hydrologic systems in most western basins have been altered for some time. Southern California basins are some of the most manipulated in the world. Population growth and an increased demand for water in arid to semiarid urban areas will cause more modifications. The USGS through the NAWQA program and other national and district programs has the resources to address this topic, including consistent data sets and methodologies, as well as the spatial and temporal scope to provide a broad picture of the topic. We have a unique database that can track changes in anthropogenic compounds (pesticides and VOCs) that other agencies lack.
Who cares and why?
Federal, State, and Local agencies are monitoring water quality and setting policy for protection of water quality and use of water resources. California agencies are now calling for grants and cooperative studies on water quality and factors affecting susceptibility of public water resources to contamination. In Utah, ground-water management plans are limiting withdrawals in order to maintain a safe yield, but also to maintain ground-water quality. Cities are banding together and using the U.S. Geological Survey to study the effects of water use on the used aquifer in their area rather than disregarding the cumulative impact of their actions.
Water suppliers are responsible for both water supply and quality. Suppliers in many areas of the arid to semiarid west are investigating artificial recharge to the ground-water systems used for public supply and the importation of water to meet demand. Information from areas that have undergone various degrees of flow alteration coupled with water-quality data could provide a basis for understanding future water-quality conditions.
The public is concerned with the quality of water that they drink. Possible changes in water quality resulting from ground-water flow alteration should be considered before implementation and affecting drinking–water sources.
Selected References:
Budget:
FY 2005: feasibility and acquisition of ancillary data and preliminary data analysis
FY 2006: data analysis, interpretation, and draft report
FY 2007: report completion, review, and publication
Salary rates in FY05, FY06, and FY07 are 1.05 the previous year’s rate to account for inflation.