South Carolina Safe Yield and Flows

Recently I was fortunate enough, or unfortunate enough, depending on how you look at it, to sit in on discussions concerning withdrawals and allocating surface waters of the state of South Carolina. The South Carolina Department of Health and Environmental Control (SCDHEC) and other government agencies, municipalities, hydrogeologists, the energy and paper industries, agriculture, non-governmental organizations like the Nature Conservancy, Edisto Riverkeeper and Friends of the Edisto, and American Rivers, held several workshops in the year 2020. We heard comments and discussions on the current withdrawal and safe yield standards and captured views from these different disciplines. In layman’s terms, SCDHEC is seriously looking at the state’s surface water policies, regulations, and permitting standards regarding the health of the environment and the over-allocating or over-permitting of South Carolina’s surface water. The idea is that overdrawing surface water will negatively affect the health of South Carolina’s water bodies. 
Link to SCDHEC surface water page: https://scdhec.gov/bureau-water/surface-water-withdrawals
The Surface Water Quantity Permitting Program was established under Title 49 Chapter 4: South Carolina Surface Water Withdrawal, Permitting Use and Reporting Act in 2011. The implementing regulation R.61-119 will establish a system and rules for permitting and registering the withdrawal and use of surface water from within the state and surface waters shared with adjacent states. The permitting, registration, use, and reporting requirements for the regulated withdrawals are specified in this regulation, a regulation which applies to any person withdrawing surface water over three million (3,000,000) gallons during any one (1) month. 
Before I go any further, I must admit that there’s a wealth of terms that become essential knowledge to get the gest of this whole discussion. Humor me while I’ll only use a few key terms - like safe yield. Safe yield (SY) is defined in the 2020 SCDHEC workshops as the amount of water available for withdrawal from a particular surface water source above the minimum instream flow (MIF) or minimum water level for that surface water source. Safe yield is determined by comparing the natural and artificial replenishment of the surface water to the existing or planned consumptive and non-consumptive uses. This is one of the major ideas or terms that are on the discussion table for DHEC and perhaps lawmakers in the coming future. So, if we were to look at certain South Carolina bodies of water, say a particular river or stream, throughout the year and imagine this mapped out on a line or bar graph, the average level of this water body should stay above the safe yield level for the majority of the year. It might dance around the steady safe yield line increasing beyond the SY in the wet months and dropping below the SY line in the dryer months of the year, typically our summer and fall. But trying to ensure there will be sufficient water levels for permitters and a healthy river system gets tricky to calculate when you factor in industrial and agricultural withdrawals and naturally low water levels due to drought.  An important factor in the whole big discussion is the fact that there are many pulling water whose use currently isn’t being calculated into the SY figures. Getting the Safe Yield numbers right is of critical importance because it sets the baseline for permitted uses. SY and Mean Instream Flows (we’ll talk about that shortly) is calculated based on the flows at the USGS (United States Geological Survey) water level gauges. This leaves areas upstream and downstream with impacts that are not fully taken into account. 

Many states in the U.S. use a low flow or drought flow model that is called the 7Q10 or something comparable. 7Q10 is set by using the lowest 7-day average flow that occurs on average over a time period of 10 years. This flow standard heavily factors low water levels into the equation of how much surface water the state can permit out annually to withdrawers. Now, let’s bring in MIF or minimum instream flow because this is the standard throughout the year that DHEC is using to dish out withdrawal permits across the state: 
Minimum Instream Flow: the flow that provides an adequate supply of water at the surface water withdrawal point to maintain the biological, chemical, and physical integrity of the stream taking into account the needs of the downstream users, recreation, and navigation and that flow is set at forty (40) percent of the mean annual daily flow for January, February, March, and April; thirty (30) percent of the mean annual daily flow for May, June, and December; and twenty (20) percent of the mean annual daily flow for July through November for surface water withdrawers
Mean Annual Daily Flow (MADF): the arithmetic mean of individual daily mean discharges (streamflow) for a period representative of the historic streamflow records, using flow measurements published by USGS or as determined by other Department approved, hydrologically valid data
As you can see from the minimum instream flow definition, different months have allocated different percentages of water estimated for withdrawal; that some months will have more rain than others and with that, higher possible withdraws - that’s pretty logical ideas, right? Exciting stuff, I know, but where this concerns an average civilian not versed in hydro-languages and flow rates is when the state continues to lease or permit out water that is already allocated. Meaning that it is possible that streams and rivers in the great state of South Carolina are currently permitted to provide more water to users than is actually in the waterbody itself. Leaving these river and streams perating at biological, chemical, and physical levels that are way below their safe yield standards.With so many users like water utilities,  industries,  energy providers, paper mills and big agriculture withdrawing water when the river or stream can not bear to lose anymore it makes one wonder is it possible to withdraw so much from a particular body of water that it is negatively impacted forever?  Not to throw big agriculture under the bus, but according to scdhec.gov, effective June 22, 2012, existing permits would be grandfathered in and agriculture will be registered not permitted if surface water use exceeds 3 million gallons in any month (100,000 gallons per day). During peak growing seasons, South Carolina law allows agricultural users, not subject to minimum flow standards, to withdraw streamflows to near zero throughout the growing season without public notice, without drought contingency plans, and without legal restrictions. It simple and unfortunate, currently  DHEC is permitting out water that South Carolina can’t afford to permit.  At times they are even over-allocating surface water to new permitted withdrawers risking damaging riverine environments and ecology for ages to come. This is an environmental, biological, chemical, water quality issue, and a big issue for the public health of South Carolina. 
Don’t take my word for it. You can read all of this and more at  https://scdhec.gov/bureau-water/surface-water-withdrawals.  One thing is for sure, South Carolinians love their recreation - fishing, birding, paddling, etc. and want healthy waterways with healthy fish, birds, and other critters thriving in them. With the state of South Carolina initiating a new Resiliency Office, could this be an appropriate starting place to ensure the state’s waterways are healthy, abundant, and able to withstand the threats of climate change and sea-level rise? 
Savannah Riverkeeper will stay engaged in with our brothers and sisters in South Carolina. This issue isn’t a new one, and solving it won’t happen overnight, but the consequences of not getting this right could haunt us for years to come.