Water Watch: Ground Monitoring Programs, Part 1

By THOMAS C. HASLEBACHER

Groundwater monitoring programs focus generally on two types of data: groundwater levels and groundwater quality. These two data types can be independent of each other depending on the size, shape and location of the groundwater basin. However, they typically are both dependent on the amount and type of recharge coming into a basin and both continually change with time.

It is the changes with time that are most important to those studying groundwater and also to those dependent on it for their water supply.

There are many reasons to initiate and maintain groundwater monitoring programs. These may include requirements from court decisions concerning water rights, regulatory compliance for contamination issues, development of groundwater flow and chemical transport models, and most importantly, management of the resource as a longterm water supply. Monitoring programs may be managed by one entity (usually governmental) or a collection of entities and/or individual stakeholders in a groundwater basin, water district or municipality.

In the case of the Indian Wells Valley groundwater basin, the bulk of groundwater level measurements are collected in March and October by the Kern County Water Agency for the Indian Wells Valley Cooperative Groundwater Management Group, Groundwater and surface water quality data collection is a joint effort shared with the IWV Water District, the Naval Air Weapons Station and the agency. These data are archived in the agency’s groundwater database.

A subset of the data from approximately 40 of the more than 300 wells monitored throughout the basin are transmitted to the California Department of Water Resources in Sacramento as part of the California Statewide Groundwater Elevation Monitoring program.

The major components of a groundwater monitoring program are:

• Competent field staff to collect and interpret the data.

• Accurate well location and well head elevation data.

• Proper data collection equipment (with routine calibration).

• Proper documentation of field data acquisition.

• Established protocol for data storage.

• Development and maintenance of a database.

• Easy access to the data by groundwater professionals.

• Regularly published interpretations of the groundwater data.

How groundwater data is stored can determine the success or failure of a groundwater monitoring program. Database software is available that can handle all aspects of groundwater data. When obtaining or building a groundwater database, ease of data input, report generation and security should be a major consideration. The agency’s groundwater-level database contains approximately 6,500 groundwater-level readings from about 330 wells. These readings range in date from 1946 through 2012. There are presently approximately 35,283 groundwater quality records in the database representing analyses from 330 wells. These readings range in date from 1952 to 2011.

Maintaining current and past groundwater-level data is crucial for use in determining trends in the surface of the groundwater (water table). These trends can be looked at from a spatial aspect (i.e., high areas versus low areas) or temporal aspect (i.e., changes in water levels in individual wells over time).

Spatial analysis of groundwater data is performed by contouring three types of groundwater level data: elevation, depth and change. This data should represent the same time frame or season. A contour is simply a line that connects points of equal value.

The winter/spring readings are most commonly used as they portray a basin’s aquifer system at its “quietest” state. Groundwater pumping is at its minimum during this time and water levels will be at their highest. During the fall, so many wells may be pumping that there may not be enough nonpumping wells to give an accurate view of the water surface. The water level in a pumping well, or one that has just turned off, will usually be considerably lower than the surrounding water table. The fall data, however, is extremely important for other interpretations.

Additionally, it is very important to know how the well is constructed (total depth and location of perforations for entrance of water into the well). Wells completed in different aquifers may have great differences in water levels. It is important to use wells completed in the aquifer that is being studied.

Next month’s article will focus on how groundwater data is analyzed and the types of contouring and other graphic analyses that can be created with the data. In addition, the importance of water quality and changes over time will be discussed.

Story First Published: 2012-12-05