Evaluating Artificial Storage and Recovery Potential of Bedell Flat, Washoe County, Nevada
Truckee Meadows Water Authority (TMWA) is a public water purveyor in northwest Nevada with responsibility for providing water to approximately 385,000 people in the Reno/Sparks metropolitan area and suburban communities north of Reno. TMWA has a conjunctive use strategy, which includes aquifer storage and recovery (ASR), to both maintain the health of local aquifers and supplement limited water resources during drought when traditional river, reservoir, and aquifer systems are being stressed. With this in mind, TMWA is considering expanding its ASR program to suitable locations.
The Bedell Flat Basin in southern Washoe County is one such location. Bedell Flat appears to have favorable hydrogeologic characteristics for an ASR implementation. The USGS Nevada Water Science Center (NVWSC) is providing technical assistance to TMWA by evaluating existing data and installing equipment for monitoring discharge and temperature of opportunistic natural flows that occur in the ephemeral Bird Springs drainage at Bedell Flat.
As populations in the western United States continue to grow, and the frequency and duration of droughts become more common, public water providers are looking to broaden their options for effective management of limited water resources. Aquifer storage and recovery (ASR) programs provide just such an option. Available surface water, imported groundwater or highly-treated reclaimed water can be stored in a suitable aquifer and recovered years later for public use during times of need, such as exceptional droughts. The NVWSC is providing technical assistance to TMWA to evaluate the feasibility for a successful ASR program in the Bedell Flat Basin.
Location of Bedell Flat, southern Washoe County, Nevada
Bedell Flat is a relatively small basin (51 mi2) with depths to water ranging from less than 5 feet in the northwest, where surface drainage exits the basin, to at least 140 feet near the middle of the basin. The alluvial materials appear favorable for ASR implementation as the basin is well-drained and nearly-impermeable playa sediments are notably absent. Although the hydrogeologic framework (thickness of basin fill, reconnaissance level groundwater recharge estimates, and estimated water budgets) has been coarsely characterized, Bedell Flat remains largely undeveloped and little is known about the groundwater system or aquifer properties.
TMWA is considering several ASR options within Bedell Flat to infiltrate recharge water, including:
- Along a natural drainage (Bird Spring Wash),
- Along an engineered infiltration gallery (Rapid Infiltration Basin), and
- Injection of potable water using injection wells.
However, before TMWA begins to make major investments in the infrastructure required for an ASR program, an understanding of the feasibility of ASR in Bedell Flat is necessary. The feasibility of artificially recharging aquifer systems by spreading water at the surface or by injection using a well depends on both geologic and hydraulic characteristics of the aquifer and should consider several factors:
- Availability and quality of water being recharged.
- Availability of adequate storage in the aquifer.
- Recoverability of stored water.
Artificial recharge programs must consider the capability of unsaturated material to accept the additional source of water. Additionally, aquifer storage and recovery efficiency can be affected by possible degradation of aquifer properties due to chemical reactions between recharged and native waters. Other common water quality concerns with ASR projects are elevated concentrations of dissolved solids and major ions.
Data Collection
The first step in evaluating the feasibility of this ASR program is to identify and evaluate existing data and install equipment to monitor the discharge and temperature of any opportunistic natural flows that may occur in the ephemeral Bird Springs drainage.
Temperature and Pressure Sensors and Engineered Flumes
NVWSC has installed temperature probes and Parshall flumes with pressure transducers along Bird Springs drainage to take advantage of any opportunistic ephemeral flow that may occur in the natural channel from precipitation events during calendar year 2016 and 2018. Any flow events would provide some of the information needed to evaluate infiltration rates along the natural drainage. Temperature and pressure data collected from transects along the Bird Springs drainage will be used to calibrate an unsaturated flow model for estimating infiltration rates and moisture content below the channel. However, long-term monitoring of these transects may also serve to identify later reductions in seepage rates due to sediment clogging.
Monitoring Wells and Borehole Geophysical Logs
Installation of monitoring wells near existing wells that can be pumped are needed to evaluate transmissivity and storage properties derived from aquifer tests. Additional wells near areas of recharge would greatly contribute to evaluating ASR potential. Monitoring wells would also be used for identifying subsurface lithology, water-level and water quality monitoring, and would be instrumented with pressure transducers. Geophysical logs should be collected with any drilled boreholes and wells. Details on number, design, and location of observation wells will be determined in consultation with TMWA as well as borehole geophysical parameters, and water quality parameters that should be collected.
Truckee Meadows Water Authority (TMWA) is a public water purveyor in northwest Nevada with responsibility for providing water to approximately 385,000 people in the Reno/Sparks metropolitan area and suburban communities north of Reno. TMWA has a conjunctive use strategy, which includes aquifer storage and recovery (ASR), to both maintain the health of local aquifers and supplement limited water resources during drought when traditional river, reservoir, and aquifer systems are being stressed. With this in mind, TMWA is considering expanding its ASR program to suitable locations.
The Bedell Flat Basin in southern Washoe County is one such location. Bedell Flat appears to have favorable hydrogeologic characteristics for an ASR implementation. The USGS Nevada Water Science Center (NVWSC) is providing technical assistance to TMWA by evaluating existing data and installing equipment for monitoring discharge and temperature of opportunistic natural flows that occur in the ephemeral Bird Springs drainage at Bedell Flat.
As populations in the western United States continue to grow, and the frequency and duration of droughts become more common, public water providers are looking to broaden their options for effective management of limited water resources. Aquifer storage and recovery (ASR) programs provide just such an option. Available surface water, imported groundwater or highly-treated reclaimed water can be stored in a suitable aquifer and recovered years later for public use during times of need, such as exceptional droughts. The NVWSC is providing technical assistance to TMWA to evaluate the feasibility for a successful ASR program in the Bedell Flat Basin.
Location of Bedell Flat, southern Washoe County, Nevada
Bedell Flat is a relatively small basin (51 mi2) with depths to water ranging from less than 5 feet in the northwest, where surface drainage exits the basin, to at least 140 feet near the middle of the basin. The alluvial materials appear favorable for ASR implementation as the basin is well-drained and nearly-impermeable playa sediments are notably absent. Although the hydrogeologic framework (thickness of basin fill, reconnaissance level groundwater recharge estimates, and estimated water budgets) has been coarsely characterized, Bedell Flat remains largely undeveloped and little is known about the groundwater system or aquifer properties.
TMWA is considering several ASR options within Bedell Flat to infiltrate recharge water, including:
- Along a natural drainage (Bird Spring Wash),
- Along an engineered infiltration gallery (Rapid Infiltration Basin), and
- Injection of potable water using injection wells.
However, before TMWA begins to make major investments in the infrastructure required for an ASR program, an understanding of the feasibility of ASR in Bedell Flat is necessary. The feasibility of artificially recharging aquifer systems by spreading water at the surface or by injection using a well depends on both geologic and hydraulic characteristics of the aquifer and should consider several factors:
- Availability and quality of water being recharged.
- Availability of adequate storage in the aquifer.
- Recoverability of stored water.
Artificial recharge programs must consider the capability of unsaturated material to accept the additional source of water. Additionally, aquifer storage and recovery efficiency can be affected by possible degradation of aquifer properties due to chemical reactions between recharged and native waters. Other common water quality concerns with ASR projects are elevated concentrations of dissolved solids and major ions.
Data Collection
The first step in evaluating the feasibility of this ASR program is to identify and evaluate existing data and install equipment to monitor the discharge and temperature of any opportunistic natural flows that may occur in the ephemeral Bird Springs drainage.
Temperature and Pressure Sensors and Engineered Flumes
NVWSC has installed temperature probes and Parshall flumes with pressure transducers along Bird Springs drainage to take advantage of any opportunistic ephemeral flow that may occur in the natural channel from precipitation events during calendar year 2016 and 2018. Any flow events would provide some of the information needed to evaluate infiltration rates along the natural drainage. Temperature and pressure data collected from transects along the Bird Springs drainage will be used to calibrate an unsaturated flow model for estimating infiltration rates and moisture content below the channel. However, long-term monitoring of these transects may also serve to identify later reductions in seepage rates due to sediment clogging.
Monitoring Wells and Borehole Geophysical Logs
Installation of monitoring wells near existing wells that can be pumped are needed to evaluate transmissivity and storage properties derived from aquifer tests. Additional wells near areas of recharge would greatly contribute to evaluating ASR potential. Monitoring wells would also be used for identifying subsurface lithology, water-level and water quality monitoring, and would be instrumented with pressure transducers. Geophysical logs should be collected with any drilled boreholes and wells. Details on number, design, and location of observation wells will be determined in consultation with TMWA as well as borehole geophysical parameters, and water quality parameters that should be collected.