A comprehensive, centrally located, publicly accessible hydrologic database is a valuable tool for Federal agencies to monitor and manage groundwater resources and to identify changing conditions caused by an increase in water use that may affect sensitive desert ecosystems. The federal agencies that manage land in Clark County currently do not use a centralized, publicly accessible database to store their hydrologic data.

USGS maintains NWIS which includes GWSI and QWDATA databases, portions of which are publicly accessible via NWISWeb. USGS will use NWIS to provide BLM, NPS, USFWS, USFS and the public with a central, publically accessible, database for hydrologic data for springs and wells on Federal lands in Clark County, Nevada.

Research Plan

BLM has requested that the USGS assist in

• compiling existing data,
• entering the data into NWIS,
• analyzing the data to identify “data gaps,” and
• collecting new data to help fill those gaps.

Two data gaps are known to exist for wells and springs:

• Water-Quality Data: Water samples will be collected and analyzed from selected springs and wells on public lands throughout Clark County. physical and chemical properties such as water temperature, pH, specific conductance, alkalinity, and dissolved oxygen will be measured in the field when sites and conditions allow.
• Accurate Location Data: The location of springs and wells will be surveyed with differential and standard GpS. Every site visited will be surveyed with a handheld GpS receiver and selected sites will be surveyed using differential techniques. Differential GpS surveys use a combination of real-time kinematic and static-mode methods that provide a field horizontal accuracy of at least 3 centimeters and vertical accuracy of at least 5 centimeters.

Data

Since the project began, the following changes have been made to sites in NWIS:

• 11 duplicate sites have been deleted,
• 10 springs and 25 wells have been created,
• about 50 sites have had their location data updated,
• 44 NV well log numbers have been added,
• over 1,100 water levels have been added. and
• 15 years of continuous and periodic water-level data have been added.

Of the 370 sites in the study area, 241 have been visited, 13 are either lost or have bad locations and are actually out of the study area, and 116 sites have not been visited.

Background

Federal land-management agencies, including BLM, NpS, USFWS, and USFS manage over 85 percent of the land in Clark County, Nevada. For sound management of natural resources, it is important to recognize the potential impacts of urban growth, particularly on springs and their associated ecosystems. To best recognize growth-related impacts and protect natural resources, it is important to establish county-wide baseline datasets to determine the current hydrologic conditions and to better recognize when these conditions are changing. Moreover, the hydrology of Clark County is complex and a comprehensive database is critical to understanding regional hydrologic issues.
 
Federal land managers have recognized three hydrologic “data gaps” in Clark County:

1. Some springs and wells lack data, are not monitored, or have never been inventoried adequately. Springs in Clark County provide water that sustains sensitive aquatic, riparian, and phreatophytic ecosystems. Although relatively small in areal extent, these ecosystems provide habitats for a diversity of plant and animal species, many of which are endemic or federally listed as threatened or endangered. Spring areas also are used for a variety of recreational activities. Spring data, including the location of springs, their physical characteristics, and discharge measurements, are useful for better understanding of the aquifer systems in southern Nevada, evaluating the distribution and rates of ground-water recharge and discharge, in developing basin and regional ground-water budgets, and monitoring the health of spring-related ecosystems. Well data and water-level measurements provide valuable information about basin and regional aquifers systems, and lithologic and geophysical logs from those wells provide three-dimensional hydrogeologic data.

1. Water-quality data are sparse or non-existent for some sites. For springs, existing data typically include field parameters (temperature, specific conductance, dissolved oxygen, and pH) whereas isotopic, bacteria, and other water-chemistry data are missing. Most springs do not have temporal water-quality data, which is critical for recognizing changing hydrologic conditions. Water-quality data for wells are also sparse, both temporally and spatially.

1. The accuracy of some spring and well location and altitude data are unknown. Accurate location and altitude data for sites improves the quality of spatial data, which is critical for desert hydrology, where spring discharge is sensitive to relatively small changes in water-levels.