Kreye 1K. Wei Ministry of Environment Province of British Columbia Abstract A map-based aquifer classification system has been developed to support ground water management in the Province of British Columbia. The system classifies aquifers on the basis of their level of development and vulnerability to contamination and provides ranking values for aquifers using hydrogeologic and water use criteria.
General characteristics[ edit ] The deposition of aquifer material dates back two to six million years, from the late Miocene to early Pliocene ages when the southern Rocky Mountains were still tectonically active. From the uplands to the west, rivers and streams cut channels in a generally west to east or southeast direction.
Erosion of the Rockies provided alluvial and aeolian sediment that filled the ancient channels and eventually covered the entire area of the present-day aquifer, forming the water-bearing Ogallala Formation.
The major differences are time and depth. The depth of the Ogallala varies with the shape of then-prevailing surface, being deepest where it fills ancient valleys and channels.
The Ogallala Formation consists mostly of coarse sedimentary rocks in its deeper sections, which transition upward into finer-grained material. Its deepest part is ft. Present-day recharge of the aquifer with fresh water occurs at an exceedingly slow rate, suggesting that much of the water in its pore spaces is paleowaterdating back to the most recent ice age and probably earlier.
Groundwater within the Ogallala generally flows from west to east at an average rate of a foot per day. Hydraulic conductivityor the ability for a fluid water to move through porous material, ranges from 25 to feet 7. Nitrate levels generally meet USGS water quality standards, but continue to gradually increase over time.
Aquifer water balance[ edit ] An aquifer is a groundwater storage reservoir in the water cycle. While groundwater is a renewable source, reserves replenish relatively slowly.
The USGS has performed several studies of the aquifer, to determine what is coming in groundwater recharge from the surfacewhat is leaving water pumped out and baseflow to streamsand what the net changes in storage are rise, fall or no change.
Many farmers in the Texas High Plainswhich rely particularly on the underground source, are now turning away from irrigated agriculture as they become aware of the hazards of overpumping.
Much of the plains region is semiaridwith steady winds that hasten evaporation of surface water and precipitation. In many locations, the aquifer is overlain, in the vadose zonewith a shallow layer of caliche that is practically impermeable ; this limits the amount of water able to recharge the aquifer from the land surface.
However, the soil of the playa lakes is different and not lined with caliche, making these some of the few areas where the aquifer can recharge. The destruction of playas by farmers and development decreases the available recharge area. The prevalence of the caliche is partly due to the ready evaporation of soil moisture and the semiarid climate; the aridity increases the amount of evaporation, which in turn increases the amount of caliche in the soil.
Both mechanisms reduce the amount of recharge water that reaches the water table. Recharge in the aquifer ranges from 0. The success of large-scale farming in areas that do not have adequate precipitation and do not always have perennial surface water for diversion has depended heavily on pumping groundwater for irrigation.
Early settlers of the semiarid High Plains were plagued by crop failures due to cycles of droughtculminating in the disastrous Dust Bowl of the s. Only after World War IIwhen center pivot irrigation became available, was the land mass of the High Plains aquifer system transformed into one of the most agriculturally productive regions in the world.
Change in groundwater storage[ edit ] Ground water levels decline when the rate of extraction by irrigation exceeds the rate of recharge. In extreme cases, the deepening of wells was required to reach the steadily falling water table.
In the 21st century, recognition of the significance of the aquifer has led to increased coverage from regional and international journalists.
In other areas, such as parts of eastern and central Nebraska and of the region south of Lubbock, Texaswater levels have risen since Sixty years of intensive farming using huge center-pivot irrigators has emptied parts of the High Plains Aquifer.
With the use of center-pivot irrigation, nearly three million acres of land were irrigated.Existing studies on the impacts of climate change on groundwater recharge are either global or basin/location-specific.
The global studies lack the specificity to inform decision making, while the local studies do little to clarify potential changes over large regions (major river basins, states, or groups of states), a scale often important in the development of water policy.
Integrated Water Resources Management (IWRM). Water is a key driver of economic and social development while it also has a basic function in maintaining the integrity of the natural environment.
Principal Karst Aquifers of the United States. Click on an aquifer to find out more information about it, or choose from the list of aquifers. resulting in highly variable karst-aquifer characteristics.
Includes the Great Valley aquifer, an important water resource for many cities. You can also view and print a fact sheet on testing your home's drinking water.. Top of Page.
Reduce Your Exposure to Lead in Drinking Water at Home. Use . This page is being updated. Thank you for your interest in this topic. We are currently updating our website to reflect EPA's priorities under the leadership of President Trump and Administrator Pruitt.
The Ogallala Aquifer is a shallow water table aquifer surrounded by sand, silt, clay and gravel located beneath the Great Plains in the United States. One of the world's largest aquifers, it underlies an area of approximately , sq mi (, km 2) in portions of eight states (South Dakota, Nebraska, Wyoming, Colorado, Kansas, Oklahoma, New Mexico, and Texas).