Enhanced Aquifer Recharge (EAR)

Guy Sewell, Ph.D., Oka’ InstituteWayne Kellogg, PG, Chickasaw Nation

Randall Ross, Ph.D., USEPA

The hydrologic cycle controls groundwater and surface water flow.

Hypothetical hydrograph showing the relative contribution to stream flow from storm flow and base flow.

Q = Q0e-kt

Human Impact on Landscape

Base Flow Dominant Condition Characteristics

• Conditions of Scarcity

– High demand, lower availability

• Ecosystem Function

– Minimal in stream flow conditions

• Falling Water Table

– Well impacts: cost, availability

– Related to available soil moisture

• Riparian Rights Issues

Can We Modify Baseflow Dynamics?

• Yes, we already do in negative direction. Reversing land use patterns is possible but may not be feasible.

• Add to ground water mass?

Aquifer RechargeAquifer Storage and Recovery

• AR is used solely to replenish water in aquifers• Mobility control: contaminants, saltwater• Control land subsidence

• ASR is used to store water which is later recovered for reuse– Drinking water supplies– Irrigation– Ecosystem restoration projects (e.g., Comprehensive Everglades

Restoration Project in Florida)

Conventional methods of AR and ASR include:– Surface spreading– Infiltration pits and basins– Injection wells

https://www.epa.gov/uic/aquifer-recharge-and-aquifer-storage-and-recovery

How is this applicable to GW/SW systems in rural Oklahoma?

• Ideal Characteristics

– Low tech/low cost

– Distributed system

– Compatible with rural application and use

– Cultural acceptance

– Cost benefit balance

Oklahoma Land Use Patterns

U.S. Department of Agriculture.2012 National Resources Inventory.

Land Cover/Use

Area (acres) Area (mi2)% Total Area

Developed 2,187,300 3,400 5%

Rural 40,267,800 63,000 95%

Total 42,455,100 66,000* 100%

*total non-Federal

Aging Flood Control Dams

The NRCS and partners, have constructed over 10,450 upstream flood control dams in 47 states. Some of these projects are reaching the end of their 50-year design life. Some dams pose a threat to the public health and safety of community residents while others have potential for creating adverse environmental impacts in downstream floodplains.

Figure 2: Hypothetical hydrograph showing the relative contribution to stream flow from storm flow and base flow.

Figure 3: Comparison of discharge curves in native and EAR implemented system.

Edwards aquifer recharge structure. Pneumatic valve opens after peak flow to reduce impact to water quality from surficial debris and sediment.

Low Water Dam

Stream Flow

Stream Flow

Constructed Watershed

Settling Basin

Dual Pond Design

Dual Pond Design: Overhead View

Aquifer RechargeAquifer Storage and Recovery

• As of 2007, nine states require water used for AR and ASR injection be potable or treated to national or state standards. Potable water is defined differently in each state. Generally, "potable" refers to water of high quality posing no health risk when consumed.

• Some primacy states allow additional types of water to be used in AR and ASR, including:

• Treated effluent

• Untreated surface and ground water

• Reclaimed water

https://www.epa.gov/uic/aquifer-recharge-and-aquifer-storage-and-recovery

A Proposed Regulatory Framework

• Enhancing a Native Process

• Passive Design

• Similar to Pervious Pavement?

– Lower Risk

– Urban Storm Water vs Rural Storm Flow

• Water Design/Best Practices

• Land Owner Tradable Credits

– Similar to severable water rights

On-going EAR Research

• Research Objectives

– Evaluate System Performance

• Hydrogeologic impacts

• Water Quality Impacts

• Evaluate Cost/Benefit

– Develop Site Selection Criteria

– Propose Policy Support (Science to Policy)

– Develop and Produce “EAR Best Practices”

On-going EAR Research

• Test Site Characterization

– Mapping

– Tracer Tests

– Monitoring Infrastructure

• System Design

• System Performance

Supporting Materials

Thank You

Type Operational Non-Functional

Plugged and Abandoned

Project Sites

ASR 542 14 65 307

AR 661 0 375 441

Total 1203 14 440 748

US-EPA Data2009

UIC regulations for AR and ASR wells

• EPA and states regulate AR and ASR wells as Class V injection wells. AR and ASR well owners or operators submit basic well information to either EPA or the state. EPA may directly implement a program, or a state may have primary enforcement authority, or "primacy."

The well is typically authorized by rule if both:

The owner or operator submits the well information

The well injection does not endanger a USDW

“no owner or operator shall construct, operate, maintain, convert, plug, abandon, or conduct any other injection activity in a manner that allows the movement of fluid containing any contaminant into underground sources of drinking water, if the presence of that contaminant may cause a violation of any primary drinking water regulation under 40 CFR part 142 or may otherwise adversely affect the health of persons.” (40 CFR 144.12L)