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Hydrologic Monitoring

Hydrologic Monitoring Network

The Las Vegas Valley Groundwater Management Program Hydrologic Monitoring Network (GMP-HMN) was established to help inform well owners about hydrologic conditions in the valley and to provide well owners an opportunity to observe fluctuations in water levels at monitoring locations near their wells.

The GMP-HMN is composed of 16 wells completed in both the principal aquifer and shallow groundwater system at locations shown on the map. These wells augment other extensive water-level monitoring networks in the valley which are measured by different agencies for the purposes of monitoring hydrologic conditions and managing groundwater quality and water resources.

What is the purpose of groundwater monitoring networks?
Monitoring networks are established and maintained to observe water level changes in the groundwater system over time to help understand the hydrologic properties and conditions in a given aquifer. The changes that are observed may be natural variations such as changes in precipitation or may be caused by human activities such as pumping or groundwater recharge programs. Once a monitoring site has enough data to establish a historical record, long-term water level trends and ranges can be projected.

How are the wells monitored?
The wells within the network include dedicated monitor wells, unused or inactive water wells, and active production and recharge wells. The physical construction specifications including the location, depth, and screened interval of the well determines the portion of the aquifer system being monitored.

The wells are monitored by physically measuring the water level using an electronic tape which indicates depth to water to within 0.01 feet. Many wells are also equipped with a pressure transducer which is a sensor that measures changes in water levels continuously on an hourly basis. The data from the transducer is stored in a data logger which is then downloaded on a regular basis by hydrologists. The data from the GMP-HMN wells are uploaded to the web site quarterly.

The water levels within the principal aquifer are active with short term, seasonal, annual, and decade-long variations observed. Hourly and daily data can record variations in barometric pressure. This type of data is usually measured with units less than a foot. Water level variation from cyclic daily and seasonal production of nearby water wells can be observed from less than a foot to tens of feet. Increased long-term water levels from the artificial recharge program first implemented in 1989 can also be observed. Other unique events such as quick small water level changes associated with earthquakes can also be observed.

How is water level data presented?
Water level data are plotted as depth to water on the vertical axis against time on the horizontal axis. The plots are referred to as hydrographs. Positive values for depth indicate water level below land surface. Negative values for depth indicate water level above ground surface or flowing (if well cap was open) artesian conditions. Water levels can also be presented as elevation to determine groundwater flow direction between similar constructed wells.

Depth to water