Groundwater Supply Availability January 2014. The Arkansas Water Plan Update Requires Assessment of...
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Transcript of Groundwater Supply Availability January 2014. The Arkansas Water Plan Update Requires Assessment of...
Comprehensive Update of the Arkansas Water Plan
Groundwater Supply Availability
January 2014
The Arkansas Water Plan Update Requires Assessment of Current And Future Water Supply Availability
Groundwater
AvailabilityGroundwaterAvailability
GroundwaterQuality
Fish and Wildlife Flows
Quality
Surface Water
What Constrains our Ability to Supply Water?
Available Supply
Water Law/Regulatory
Physical Availability
Infrastructure
Groundwater Availability
Arkansas Groundwater Demand Data Trends
1935 1955 1975 1995 2015 2035 20550
1,0002,0003,0004,0005,0006,0007,0008,0009,000
10,0007,934
8,566
8,9809,055
9,074
Historic Groundwater Use Projected Groundwater Use
Gro
undw
ater
Dem
and
(MG
D)
Updated Demand Data Added from 2010-2050
~ 13% increase
Comparison of Demand and Achievable Pumping Rate
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Groundwater Modeling Scenarios Scenario 1 and 2:
Minimum water elevation equal to the bottom elevation of both unconfined and confined aquifers for wet and dry climate conditions
Scenario 3 and 4: Minimum water elevation equal to half the aquifer thickness in the alluvial aquifer and the top of formation in the confined aquifer for wet and dry climate conditions
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Interior Highlands of Northern and Western Arkansas Qualitative Evaluation of Water Supply
Availability
Groundwater use has declined and surface water use has increased dramatically, and the vast majority of the population in northern Arkansas is served by surface water
Various aquifers generally occur in shallow, fractured, well-indurated, structurally modified bedrock
Many formations are capable of supplying volumes sufficient for small community-supply sources of water
Northern Interior Highlands AquifersSpringfield Plateau Aquifer
Widely used throughout its extent in northwestern ArkansasNumerous domestic and livestock wells, although surface-water
systems have replaced the aquifer as a general source of water supplyOzark Aquifer
Primary use of the Ozark aquifer is for public supply; 76 MGD was withdrawn for public supply in 2010
Irrigation use was about 20 MGD from the Ozark aquifers in 2010; 70% of irrigation occurs in counties in the aquifer’s far eastern extent, where row crops like cotton, rice, and soybeans are commonly grown
Depth to water in most of these wells is approximately 100 ft
Southern Interior Highlands AquifersArkansas River Valley Alluvial Aquifer
Irrigation pumpage is smallMunicipal supply withdrawals induce recharge from the river
Ouachita Mountains AquiferShould not be considered as a source of supply for municipal growth
and economic development unless the required quantity was smallWestern Interior Plains Confining System
Well yields sufficient only for household, small municipal, and non-irrigation farm use.
Groundwater Quality
Groundwater Quality Analyses
Groundwater quality information provided by USGS
Groundwater Quality MethodologyWater quality data from approximately 8,000 groundwater
sites: 7000 from the ANRC and USGS database1,000 from the ADEQ database
Statistical analyses and spatial distribution maps for chemical constituents associated with 16 aquifer systems in Arkansas.
Major ions (calcium, magnesium, sodium, potassium, chloride, sulfate, and bicarbonate) and selected trace metals (iron, manganese, and arsenic).
Drinking Water StandardsWater quality of drinking water will be compared to:US EPA drinking water standards (Maximum Contaminant
Levels (MCL))Health advisories Secondary drinking water regulations for cosmetic effects
(such as tooth or skin discoloration) or aesthetic effects (such as taste, odor, or color)
East Regional Planning AreaMississippi River Valley alluvial aquifer
Water quality generally is goodElevated iron concentrations in most areas prevent use for commercial,
industrial, and municipal without treatmentElevated salinity additionally occurs in different areas of eastern
Arkansas
Cockfield aquifer Principal aquifer in southeast Arkansas In outcrop area, lower pH values and dissolved solids but higher nitrate
and iron concentrationsDowndip higher pH and dissolved solids; lower concentrations of
nitrate and iron
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East Regional Planning AreaSparta aquifer
Second highest of volume of useGenerally is of very high quality Isolated areas contain slightly elevated chloride concentrations Downdip increases in dissolved solids and decreases in iron and nitrate
Cane River, Carrizo, Wilcox, Nacatoch, Ozan, Tokio, and Trinity aquifersIncreasing salinity at various distances downdip from the outcrop
areas that renders the groundwater unusable for most purposes.
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North Regional Planning AreaOzark and Springfield Plateau aquifers
Rapid influx of surface-derived contaminants, especially nitrogen, in karst landscape
Nutrients, bacteria, and other surface-derived contaminants associated with agricultural activities pose the greatest threat to groundwater quality
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West-central, South-central, and Southwest Regional Planning AreasOuachita aquifer and the Western Interior Plains
Dominant changes in geochemistry were attributed to rock type, residence time along individual flow paths, and resultant rock- water interaction
Elevated iron and manganese concentrations and production of methane
Nutrients, bacteria, and other surface-derived contaminants pose the greatest threat to groundwater quality
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