Groundwater
Significance
Overview
Groundwater is an important part of the hydrological cycle. This is water stored underground in the soil, or in the pores and crevices of rocks.
Information from The Groundwater Project Website, suggests that groundwater makes up 99% of the liquid fresh water on Earth. It is a vital water supply for humanity and also sustains rivers, lakes, wetlands and ecological systems. [1]
According to the USGS,
"Groundwater moves slowly, typically at rates of 7-60 centimeters (3-25 inches) per day in an aquifer. As a result, water could remain in an aquifer for hundreds or thousands of years. Groundwater is the source of about 40 percent of water used for public supplies and about 39 percent of water used for agriculture in the United States." [2]
Why Monitor Groundwater Levels?
As per the Texas Groundwater Protection Committee website, groundwater is a vast resource and very important to the State of Texas.
"There are thirty major and minor aquifers in the state that range from shallow, unconsolidated sand and gravel deposits underlying river valleys to deep rock aquifers that cover large parts of the state.
Of the 16.1 million acre-feet of water used in Texas in 2008, groundwater contributed 9.7 million acre-feet, or about 60 percent, with surface water supplying the rest."
The Texas Water Development Board (TWDB) and local Groundwater Conservation Districts
(GCDs) are constantly monitoring water levels statewide to detect changes in usage, to develop groundwater availability models and to be able to identify locations where ground water use is occurring at unsustainable rates.
These actions will assist the relevant authorities in "planning to meet future demands for water." [3]
The Relationship Between Water Levels in Wells and Groundwater Quality and Quantity.
Ground water quality is influenced by several different variables, including: "aquifer rock type, soluble minerals present and their concentration, groundwater flow paths through the aquifer, contact or residence time and recharge rates."
Groundwater quality reflects very few changes in relation to water level fluctuations, as water level is influenced by "groundwater recharge and discharge to and from aquifers." Water level changes are based on the volume of water that is drawn out, the volume of water being fed into the aquifer from sources such as rainfall runoff and the volume of water that is stored in the aquifer at any given time.
There are situations where changes in water level can severely impact water quality. This includes when the pumping out of water from a groundwater well, reverses hydraulic gradient leading to salt water encroachment into aquifers. This can lead to “salinity levels above the drinking standards which is detrimental to groundwater quality,” and would require additional treatment to be potable.[4]
What is a monitoring well?
Information provided by the Texas Groundwater Protection Committee website states:
By definition in Texas Water Code § 27.002, a “Monitoring well means a well that is used to measure or monitor the level, quality, quantity, or movement of subsurface water.”
"Monitoring wells can either be specifically drilled for monitoring groundwater or may be preexisting domestic or public-supply wells that are also used for monitoring.
Monitoring wells are used to collect groundwater data for scientific studies and to make environmental regulatory decisions. Scientific uses include the collection of water quality and biological samples, water-level measurements and tracer studies." [5]
Credits
Information presented on this page was obtained from The Texas Groundwater Protection Committee (TGPC) website