Monday, August 15, 2016

Vanishing Groundwater

From  Famiglietti and Rodell 
In the August National Geographic is an article with great pictures about the Ogallala aquifer. The High Plains aquifer in the central United States running from South Dakota through Nebraska, Kansas, Colorado, New Mexico, Oklahoma to Texas is commonly known as the Ogallala aquifer (because the Ogallala formation makes up about three quarters of the aquifer) became news and burst into public awareness due to the protests associated with the Keystone XL Pipeline.

As highlighted by National Geographic there is a much bigger threat to the Ogallala; the aquifer is being depleted because the groundwater within much of it is predominately non-renewable. The groundwater aquifer that spans and estimated 174,000 square miles is the primary source of water for the High Plains. This was open range land until the groundwater from the aquifer was used to turn the range land into irrigated crops. However, according to John Opie in “Ogallala: Water for a Dry Land” this is essentially fossil water that was generated 10,000-25,000 years ago by the melting of the glaciers of the Rockies.

Groundwater laws and regulations vary by state. In Kansas and Nebraska the state owns the groundwater and rights to use the water were granted (in perpetuity) to property owners. Unfortunately, like water rights elsewhere rights granted for use often exceed water available. Where water is wealth, this happens over and over again. In Texas as in Virginia any groundwater you can pump from under your land is yours by right. Though the states are monitoring water usage, they do not have the political will to cut usage. While in Virginia we could limit use of groundwater to a level that would be sustainable, our aquifers are young and recharging; the High Plains aquifer could only manage the depletion of the aquifer. Farmers are selling their water in the form of cheap corn for ethanol, and their grandchildren or possibly even their children will have no water to farm. Everyone wants someone else to stop pumping groundwater. It does not seem possible to regulate and control private wells.

Science now can demonstrate the depletion. The Gravity Recovery and Climate Experiment (GRACE) and Global Land Data Assimilation System (GLDAS) to quantify groundwater depletion are satellites that are used to measure changes in gravity caused by moisture. The satellites are used to measure monthly changes in total earth water storage by converting observed gravity anomalies they measure from space into changes of equivalent water content. This method of converting the gravity data to water data was developed by Matthew Rodell & James S. Famiglietti in 1999. Dr. Famiglietti and Dr. Rodell and a group of researchers at the University of California, Irvine, the University of Texas, and the Hydrological Sciences Branch at NASA GSFC have worked in partnership to apply GRACE and GLDAS to perform real world groundwater monitoring. NASA has been collecting data for more than 13 years. Last year they published two papers using the first 10 years of collected data to quantify groundwater use, resilience and stability. The news was not good.

Though, ten years of data may not be adequate to determine accurate changes in water availability and groundwater recharge. Using GRACE data, Drs. Famiglietti and Rodell identified what appear to be  areas of water depletion in the United States. These areas include the important food producing regions in California’s Central Valley, and the southern High Plains (the southern part of the Ogallala); large areas of the southeastern U. S. that has been plagued by persistent drought, including Alabama, and portions of the Mid-Atlantic region. Based on the data since 2003, the wetter, northern half of the U.S. has become wetter, while the drier, southern half has become generally drier. As seen in the diagram above, Virginia’s aquifers are under stress. It is difficult to undo water dependent development; however, it is essential that we prevent further development that would impact water sustainability.

On the most local level, Prince William county, we need to examine the sustainability of water resources as an essential part of the Comprehensive Plan. The current version of the comprehensive plan does not even consider water sustainability, and only mentions the Rural Crescent as requiring each single family home to have 10 acres. The basic zoning that exists now in the Rural Crescent is A1- agricultural, allowing one house per 10 acres. The real problem is that highest and best use of the land in the current environment is developing homes. Cutting up the rural crescent into 10 acre parcels or building large churches, schools or even random clustered developments reduces the groundwater recharge, increases the demand for water, increase the potential for contamination, erodes the land by increasing the stormwater velocity over pavement, roadways, buildings and increases sediment flow into our rivers and our Bay.

Whether or not continued residential growth will seriously deplete groundwater supplies is an open issue that has not been studied. But the failure of groundwater supplies or extensive contamination as has happened in areas of Fairfax and Loudoun Counties; however, could destroy property values (after all who buys a house without running water?) and lead to enormous additional costs to homeowners and taxpayers and a lower quality of life for all. Loudoun Water is spending tens of millions of dollars to solve the water problems in Raspberry Falls and Selma communities alone that they are charging to all water customers.

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