1. Comprehensive Update of the Arkansas Water Plan
Groundwater Supply Availability
January 2014

2. The Arkansas Water Plan Update Requires Assessment of Current And Future Water Supply Availability
Groundwater
Surface Water
Groundwater
Availability
Availability
Fish and Wildlife
Flows
What are the capacities of the water resources on which our citizens rely?
Data summaries
Simulation models
Criteria to indicate unacceptable impact
Current conditions for baseline assessment
Apply future demands and management practices
Groundwater
Quality
Quality

3. What Constrains our Ability to Supply Water?
Available Supply
Water Law/Regulatory
Physical Availability
Infrastructure

4. Groundwater Availability

7. Arkansas Groundwater Demand Data Trends
Updated Demand Data Added from
~ 13% increase

8. Comparison of Demand and Achievable Pumping Rate

9. The individual 10-year demand projections were used for each of the respective periods.
The pumping in Arkansas was represented with 51,351 individual well locations. In many cases, more than one well was located in a single model cell.
The total groundwater demand across all aquifers ranges from 7,800 mgd in the base period, increasing to 8,900 mgd in 2050.
Production from the alluvial aquifer comprises 97.5 percent of the total pumping, with about 2 percent from the Sparta and the remaining 0.5 percent from the Wilcox aquifer.

10. 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

15. 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

16. Northern Interior Highlands Aquifers
Springfield Plateau Aquifer
Widely used throughout its extent in northwestern Arkansas
Numerous domestic and livestock wells, although surface-water systems have replaced the aquifer as a general source of water supply
Ozark 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

17. Southern Interior Highlands Aquifers
Arkansas River Valley Alluvial Aquifer
Irrigation pumpage is small
Municipal supply withdrawals induce recharge from the river
Ouachita Mountains Aquifer
Should not be considered as a source of supply for municipal growth and economic development unless the required quantity was small
Western Interior Plains Confining System
Well yields sufficient only for household, small municipal, and non-irrigation farm use.

18. Groundwater Quality

19. Groundwater Quality Analyses
Groundwater quality information provided by USGS

20. Groundwater Quality Methodology
Water quality data from approximately 8,000 groundwater sites:
7000 from the ANRC and USGS database
1,000 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).

21. Drinking Water Standards
Water 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)

22. East Regional Planning Area
Mississippi River Valley alluvial aquifer
Water quality generally is good
Elevated iron concentrations in most areas prevent use for commercial, industrial, and municipal without treatment
Elevated 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 concentrations
Downdip higher pH and dissolved solids; lower concentrations of nitrate and iron

23. East Regional Planning Area
Sparta aquifer
Second highest of volume of use
Generally 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 aquifers
Increasing salinity at various distances downdip from the outcrop areas that renders the groundwater unusable for most purposes.

24. North Regional Planning Area
Ozark 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

25. West-central, South-central, and Southwest Regional Planning Areas
Ouachita 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