Groundwater levels in a Calhoun and Orangeburg County aquifer in the Edisto River Basin are dropping and steps need to be taken to study and reduce the amount of water being pulled from the aquifer.
The Black Creek/Crouch Branch aquifer, located in Orangeburg and Calhoun counties, has been seeing a groundwater level decline over the past 22 years. Groundwater levels predicted through 2070 have the aquifer dropping between 5 feet and 50 feet.
The issue could become more pronounced as population grows.
“What might happen is those drawdowns of the groundwater level decreasing is that the top of the water level in that aquifer might actually drop below the sand layer that contains that water,” geologist Laura Bagwell of the Edisto River Basin Council told about 40 gathered Thursday at the Orangeburg Department of Public Utilities operations center on Sprinkle Avenue for the release of a 324-page draft plan for the Edisto River Basin. “That is something that geologists and hydrogeologists don’t like to think about. We try to avoid it if we can.”
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Bagwell said the ramifications are the sand that contains the water could densify and change so much that if water levels ever rose to the level again, there would not be any water in the area.
“In an even more extreme case, the result of overpumping or drawdown in one of these aquifers … that aquifer might densify or not be able to hold water in the future. But there might develop an area of subsidence so that the layer overlying the aquifer might actually move downward and collapse,” Bagwell said. “That is not a problem we have a lot of in South Carolina.”
Subsidence can result in infrastructure damage, increased flood risk in low-lying areas, and lasting damage to groundwater aquifers and aquatic ecosystems.
“That was a special concern for us,” Bagwell said.
Bagwell said the drawdown in the Crouch branch aquifer goes about 75 feet to 100 feet.
“In that area, that means the water level will drop below the top of the Crouch branch aquifer,” Bagwell said. “That is a bad thing.”
She said the aquifer straddles the line between the Edisto River Basin and the Santee basin.
Bagwell said recommendations to preserve the aquifer would be for some water users to switch from groundwater to surface water.
“There is always water to be saved,” she said.
Bagwell said another option would be for users to tap into another aquifer that has lesser drawdowns and is not as stressed.
“That would not be without added expense,” she said. “It takes a lot more money to drill a deeper hole.”
Bagwell said overall the state should continue to be supportive of funding science and regulatory agencies to continue to study the aquifers.
“Let us put in some new monitor wells to study this,” Bagwell said. “Let’s continue to do some groundwater modeling to study this.”
The findings and recommendations were among many released by the South Carolina Department of Natural Resources in the 324-page draft Edisto River Basin Plan.
The plan, released to Edisto River Basin stakeholders, assesses current and future water availability in the basin and documents water-management strategies that can help ensure water is available for all future uses in the basin for the next 50 years.
Edisto River Basin facilitator John Boyer provided attendees highlights of the findings and recommendations of the several-hundred-page draft.
Overall, the study shows water resources of the Edisto River Basin are generally sufficient to meet current and projected future needs.
“We really didn’t see a lot shortages or issues,” Boyer said.
Agriculture
Projected water shortages through 2070 (principally in the agricultural sector) can likely be managed with on-site (in many cases, already existing) storage, according to the study.
Existing drought-management plans, if followed, are effective in eliminating the projected infrequent, short-term public water supply shortages through 2070. The shortages are projected because of growth and water demand, according to the study.
“We saw that projected water shortages through 2070 in the agricultural sector occurred primarily on very small tributaries with no upstream withdraws,” Boyer said, noting agricultural projected water shortages “are likely overestimated.”
Boyer said when looking at impoundments that are used by agricultural operations, “there really are not shortages as predicted by the model because of the storage provided by those impoundments and their ability to get those agricultural operations through drought periods.”
Concern about agricultural use of the river by farmers arose about nine years ago when Michigan-based potato farm Walther Farms in Aiken County planned to withdraw billions of gallons of water from the South Edisto River. The company grows potatoes for Frito-Lay potato chips.
The farm initially planned to withdraw 805 million of gallons of water monthly or 6 billion gallons annually.
Its plans immediately raised alarm among environmental groups such as the Friends of the Edisto about the farm’s water usage and its impact on the river.
At the time, South Carolina Department of Health and Environmental Control officials said the river has more than enough water to accommodate the withdrawals.
Environmental groups and the farm were able to come to a compromise.
Currently users withdrawing more than 3 million gallons of surface water or groundwater in any month must either obtain a permit or register their use and report withdrawals to SCDHEC annually.
Users withdrawing less than this threshold are not required to report their withdrawals; however, they may choose to report voluntarily.
For surface water withdrawals over the threshold, agricultural water users must register their use while all other users must permit their use in accordance with DHEC’s Surface Water Withdrawal, Permitting, Use and Reporting.
Water withdrawals
Only about 17% of the allowable (permitted and registered) water volumes are currently withdrawn from surface and groundwater, according to the study. The basin would be unsustainably stressed, with frequent shortages and more severe low flows, if all allowable withdrawals were taken.
Officials say it is highly unlikely that all allowable users would withdraw given the demand projections.
“That is in fact three times more than our high-demand scenario,” Boyer said.
About 150 million gallons a day are used from the Edisto River, with agriculture and public supply being the largest users. Currently, ag users withdraw about 79 millions of gallons a day from the basin.
The projection is that water demands will increase to about 234 million gallons a day or 27% of the registered permitted users.
These projected water demands are well below the total permitted and registered withdrawal volumes in the basin of 866.4 millions of gallons a day, according to the study.
Boyer said even though a small percentage of permitted users are withdrawing water, surface water resources are over-allocated based on existing permit and registration amounts in the basin. As a result, state agencies cannot grant more surface water registrations.
Future surface water withdrawers seeking new registrations in the basin will need to apply for a permit and be subject to permit fees and conditions.
“We don’t want to have to hamstring the farmer or somebody that wants a small water use that could be registered rather than permitted to have to pay the permit fees and abide by the conditions,” Boyer said. “The ask here is not to tell farmers to stop irrigating when there is a drought. It is focused more on the larger users where most of the impact can be found in maintaining water levels.”
Streamflow/ecology
Changes in water use are not likely to impose significant risk to the ecology of the basin, though this finding is generalized over large scales, and certain headwater tributaries may be more affected than primary and secondary tributaries.
Dr. David Bishop, ERBC member and Coastland and Midlands conservation director, said the Edisto is very resilient.
“The Edisto is a flashy system,” Bishop said. “Sometimes this river dries if nobody uses it. The species that live in the Edisto can handle these sort of floods, drawdowns and that sort of thing. From a biology and ecology standpoint, the river is in good health.”
Water management in drought
- The RBC developed a low-flow management strategy that calls for voluntary, tiered curtailment by the largest surface water withdrawers when Edisto River flow declines to specified levels.
Orangeburg Department of Public Utilities Water Division Director Eric Odom said the utility makes it a focus to be good stewards of the river.
The utility has implemented leak-detection and water-loss controls as well as water audits.
“Through our water audit program, we were able to account for over 95% of the water that we pump out of our treatment plant, which we feel is a very good steward of the water that we are pulling out of the river,” Odom said.
The utility has also implemented an automated meter infrastructure or smart meter program where customers are alerted of water leaks.
On the supply side, Odom said the utility has an aquifer storage and recovery program where water is pulled out of the river, treated and then injected into wells and stored for peak times in the event of a drought. The utility also has interconnectivity with neighboring utilities for emergency supplies.
RBC member Charleston Water System Manager Jason Thompson said water management during drought is key.
“We really do believe that individual resiliency has the power to equal greater basin resiliency,” Thompson said. “The more resilient the largest withdrawers are, the more resilient the basin will be, especially during low-flow times during drought.”
Thompson said the biggest users need to be ready for times of low river flows.
He said the plan triggers based on stream flows after all withdrawals.
“The river should not run dry regardless of how severe a future drought and the river flow is split evenly between the withdrawing and non-withdrawing designated uses,” Thompson said.
Even without surface water use, flows in the river can drop below minimum instream flows during drought. The most severe drought on record for the river was in 2002.
The river at that time was about .87-feet a 90-year low.
Draft plan process, goals
The draft plan was developed over a 2-1/2-year period by the Edisto River Basin Council, a working group of stakeholders with water interests in the basin.
The group consisted of a number of different sectors, including agricultural, forestry irrigation, utility providers, environmental and conservation interests, industrial and economic development, local governments and water recreation.
Of local interest, the group had representatives from the Bamberg Soil and Water District, Bamberg Board of Public Works, Orangeburg DPU, Orangeburg County planning, Orangeburg Country Club and Orangeburg County farmer Landrum Weathers.
The goals of the plan were to develop water-use strategies, policies, and legislative recommendations for the Edisto River basin to:
- Ensure water resources are maintained to support current and future human and ecosystem needs
- Improve the resiliency of the water resources and help minimize disruptions within the basin
- Promote future development in areas with adequate water resources
- Encourage responsible land-use practices
- Develop and implement a communication plan to promote the strategies, policies and recommendations for the Edisto River Basin
The Edisto River Basin covers approximately 3,120 square miles, making up 10% of the state’s total area.
The basin extends from southeastern Edgefield County, at its northern limit, to the western portion of Charleston County at the coast. The river runs through Orangeburg, Calhoun and Bamberg counties.
The Edisto River is one of the longest free-flowing blackwater rivers in North America.
Of note, however, is the comparatively high percentage of land currently used for agriculture (21%). Farming, including the production of both crops and livestock, is vitally important to the economy in the Edisto River Basin.
The basin contains some of the most productive agricultural land in the state, according to the study.
The rivers and tributaries of the Edisto River Basin are home to 87 native and three introduced species of freshwater fish.
The Edisto River is also an important habitat for diadromous fish, those that migrate between freshwater and saltwater. Striped bass and Atlantic sturgeon can be found in various reaches of the Edisto River, depending on the season, according to the study.
The Edisto River is the largest river system completely contained within the borders of South Carolina.
The basin is composed of four major subbasins: South Fork Edisto, North Fork Edisto, Lower Edisto and Four Hole Swamp.
Water assessment plan
The state began implementing its vision for a comprehensive and actionable water plan in 2014 with the development of surface water quantity models for each of the eight major river basins in the state.
This was followed by the update of a detailed groundwater model of the Coastal Plain Aquifer System and the development of methodologies for projecting water demands for all water-use sectors.
The Edisto RBC report constitutes the first of the eight basin plans, and is organized and supported by the work of the State Water Planning Process Advisory Committee (PPAC).
This group created the South Carolina State Water Planning Framework published in 2019.
The SCSWPF now serves as a comprehensive, uniform guide for the RBCs, each charged with developing an understanding of the water resources in their respective basins; identifying the gaps or risks related to current and future water uses; and developing recommended policies, management practices, and legislative considerations “designed to ensure the surface water and groundwater resources of a river basin will be available for all uses for years to come, even under drought conditions.”
River basin plans will focus principally on the quantity and availability of surface water and groundwater for all designated uses: drinking water, agricultural and other irrigation, forestry, industry and economic development, power generation, non-consumptive uses such as aquatic habitat suitability and environmental needs, and water-based recreation.
The river basin plans are the fourth of a five-step process to update the South Carolina State Water Plan with actionable recommendations and priorities.
Collectively, all eight plans will be combined into the updated State Water Plan, which is why consistency in the planning process and types of recommendations made is important. Ultimately, the updated State Water Plan will help guide decisions to preserve water for all uses throughout the state.
The plan will be submitted the state lawmakers for final approval.
How to review, comment
The draft Edisto River Basin Plan is available for review and download at the SCDNR website at https://hydrology.dnr.sc.gov/edisto-river-basin-plan.html.
The public meeting was partly held to solicit public comments on the plan.
Public comments will be accepted from Feb. 15 through March 17.
Comments should be submitted to Clemson University via email (scwatermodels@clemson.edu), or mailed to:
SC Water Resources Center
Office: E-137, 509 Westinghouse Road, Pendleton, SC 29670
Attn: Dr. Tom Walker
The public can download a copy of the South Carolina State Water Planning Framework and learn more about the SC river basin planning process at: https://hydrology.dnr.sc.gov/state-and-river-basin-planning.html.
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