Land Use and Land Cover Changes Impact on Groundwater

Kumari Yadav S (2023) Land Cover Change and Its Impact on Groundwater Resources: Findings and Recommendations. Groundwater - New Advances and Challenges. IntechOpen. Available at: http://dx.doi.org/10.5772/intechopen.110311.

This is a book to read. The editor of the book cited above examined many of the  groundwater studies recently completed that assess the impact of Land Use and Land Cover (LULC) changes on groundwater. As you can imagine many of the impacts vary and there are tremendous gaps in our current knowledge. Below I have excerpted some of the introduction highlights. You can order a copy of the book from Amazon.

Groundwater is an essential. It serves as a buffer against short- and long-term fluctuations in surface water availability brought on by climatic variability. Approximately 2 billion people on earth depend primarily on groundwater for domestic and agricultural.  Groundwater is crucial for irrigated agriculture and for ensuring the safety of the world’s food security. Feeding mankind is the largest use of water. It accounts for 90% of freshwater consumption. The annual groundwater use for irrigation is 545 km³ of which 43% of the water used annually comes from groundwater.

In many areas, groundwater may be the sole supply of water that is always present. The use of groundwater is influenced by variables, including accessibility, transportability, cost-effectiveness, and availability. The main reasons why people choose to use groundwater water are reliable supplies and reasonable prices 

Groundwater recharge is the vertical flow of water that reaches the water table and increases groundwater storage. Rates of recharge vary by orders of magnitude over space and time, depending on the interaction of climate, soil, geology, surface hydrology, vegetation, and land use. Groundwater recharge, which occurs primarily through rainfall-recharge and surface water and groundwater interaction processes, replenishes groundwater aquifer systems. The change in LULC impacts groundwater recharge processes by modifying the earth’s hydrological system and balance.

Scientists are finding that the quantity, locations, and timing of groundwater recharge and discharge are increasingly altered due to rising population, agricultural growth, and urban land area. For groundwater development and sustainable groundwater resource management, groundwater recharge determines the groundwater withdrawal rates in a region

Land use change is a complex, dynamic process, which has direct impacts on soil, water, and the atmosphere. The most urgent problem of the twenty-first century in terms of groundwater monitoring and accurate projections is the rapidly changing Land Use and Land Cover (LULC). LULC change is becoming a major ecological concern influencing the groundwater recharge significantly. Understanding groundwater recharge in turn is necessary to determine what is a sustainable use rates and analyze aquifer sensitivity to pollution.

Groundwater quality is declining due to rising water demand, urbanization, changing land use and land cover, and climate change. Changes in LULC are among the most significant anthropogenic interventions.  LULC impacts the surface of the Earth by changing vegetation in forests, water bodies, and adding human structures.

While groundwater is an essential and significant portion of the freshwater supply for household, agricultural, and commercial applications, the effects of LULC change on groundwater recharge are not adequately understood, which leads to groundwater depletion. Therefore, understanding the impacts of LULC change on the groundwater is needed for the optimal management of natural resources.

Changes in land cover in the USA caused a rise in both the minimum and maximum temperatures. Additionally, groundwater condition (both quality and quantity) and its recharge are negatively impacted by urbanization of previous agricultural and open spaces. The hydrology of the region has been shown to have changed as a result of the conversion of natural, agricultural, and other low-population density sites into urban/suburban populations. Evidence shows that when urbanization is excessive, more than half of the precipitation drains off and just a small portion is infiltrated deeply.

The change in land cover has a significant impact on the change in groundwater recharge. Estimating groundwater recharge is crucial in managing water resources including surface water resources. It has become widely accepted that changes in LULC have an impact on groundwater. Numerous factors influence LULC change and its impact on recharge. Understanding of these processes and monitoring their impact is required to manage groundwater resources to be sustainable.

The Prince William County Board of Supervisors has once again issued a directive to staff for a groundwater study. The PW County Department of Public Works has submitted a proposal to the Prince William County Board of Supervisors for Groundwater Study to address concerns with the impact of future developments and the sustainability of groundwater as a water supply.

Last time the Department of Public Works proposed only to have the U.S. Geological Survey (USGS) create a Soil Water Balance Model and that it was not necessary or cost effective to study the actual groundwater in the various soil types in the county. This was not followed up on and was inadequate to assure sustainable water for all our residents.  Approximately 15% of Prince William County depend on groundwater for their drinking water. This includes the about 16,000 private wells in the semi rural areas of the county and the Evergreen Water District is supplied by groundwater wells.

We do know that groundwater availability varies by location even within Prince William County (Nelms and Richardson, 1990). Precipitation and soil types determines how much the shallower groundwater is recharged annually. The volume of water that can be stored is controlled by the reservoir characteristics of the subsurface rocks. We need monitoring wells spread in the areas of the county where groundwater is depended on in each of the soil types. In addition, we need the groundwater wells of commercial users to track usage. We need to ensure the sustainability of the groundwater in Prince William County. The water supply is not unlimited.