Diamond Valley Flow Systems — Phase II

The Diamond Valley Regional flow system consists of five hydrographic areas in central Nevada – Monitor Valley, Antelope Valley, Kobeh Valley, Diamond Valley and Stevens Basin.  These hydrographic areas, which cover a land area of approximately 3,110 mi², are interconnected by ephemeral streams, by subsurface flow in basin-fill aquifers, and, to a poorly understood extent, by subsurface flow in deeper carbonate-rock aquifers. The need to develop a better understanding of the regional flow system arises from (1) likely development of ground water for agriculture and mining, (2) ongoing ground-water declines in Diamond Valley, the terminus of the flow system, and (3) possible exportation of ground water for urban use.

In 2004, the USGS, Eureka, Lander, and Nye Counties and the Nevada Division of Water Resources, began a water-resources investigation to provide an understanding of the ground-water flow system. The study was divided into phases, each focusing on specific aspects of the regional flow system. Phase one, which is completed, was a two-year water-resources investigation focusing on describing the occurrence and movement of ground water and historical water-level changes in the basin-fill aquifers that underlie these valleys. The results of phase one of the study are presented in USGS Scientific Investigations Report 2006-5249 titled, "Hydrogeologic framework and ground water in basin-fill deposits of the Diamond Valley Flow System, Central Nevada". In 2006, the USGS, in cooperation with Eureka County, continued the water resources investigation of the flow system focusing on understanding the hydrogeology of each basin and refining the estimates of ground-water inflow and outflow.

Spring in Antelope Valley.

Objectives

The overall study objectives are to refine the water budgets of the basins, describe interactions between basin-fill and carbonate-rock aquifers, and evaluate the effects of future ground-water withdrawals in the study area. Phase two objectives are to refine estimates of ground-water inflow and outflow for basins that make up the Diamond Valley flow system, define the geochemical character of ground water in each basin, and develop a conceptual model of the flow system that accounts for geometry, hydraulic properties, and interconnections of basin-fill and carbonate-rock aquifers.

Strategy and Approach

Phase two will extend over a three-year period beginning in the summer of 2006. The approach will be to quantify the different ground-water inflow and outflow processes for each basin and develop a conceptual model of the flow system. Ground-water inflow consists of infiltration of precipitation and subsurface flow between basins. Infiltration has been quantified as part of another study and those results will be used to quantify inflow by precipitation infiltration in the study area. The three outflow processes—evapotranspiration (ET) from phreatophyte vegetation and irrigated crops , subsurface flow between basins  and ground-water pumping for agriculture and domestic use will also be quantified. ET will be estimated using the Bowen-ratio method. Bowen-ratio sites will be established in representative areas of ground-water discharge (phreatophyte communities, agriculture, and playas) for a period of about 18-months. This time period will include two active growing seasons (spring to summer) and help determine mean annual rates. The different areas and types of ET will be mapped using GIS analysis and field verification. The hydrogeology of each of the basins, including thickness and extent of basin-fill deposits and distribution of carbonate-rock aquifers will be evaluated using gravity and aeromagnetic data and log information from oil exploration wells. Water-quality samples will be collected from selected wells and springs using established protocols documented by the USGS. These data will be used to establish baseline chemistry of ground water and help to understand subsurface flow. Concentrations will be compared to drinking-water standards to evaluate water-quality for dissolved inorganic constituents. A USGS Scientific-Investigations Report describing the study results will be published in September 2009.

Evapotranspiration monitoring station in northern Diamond Valley.

Relevance and Benefits

The proposed study is relevant to issues one, six, and seven of the Nevada Water Science Center Science Plan. These three issues address the need to refine water budgets and to better understand evapotranspiration and regional ground-water systems. The study also is consistent with a goal of the USGS Strategic Plan, which is that of providing water-resources managers with accurate, reliable, and impartial scientific information. The work will benefit the cooperators and other water-resources agencies by providing information necessary for sound resource development and management decisions.

Publications

Tumbusch, M.T., and Plume, R.W., 2006, Hydrogeologic framework and ground water in basin fill deposits of the Diamond Valley flow system, central Nevada: U.S. Geological Survey Scientific Investigations Report 2006-5249, 38 p.