How DHEC Measures Surface Water Quality

How DHEC Measures Surface Water Quality 

Water quality monitoring data helps us understand why certain conditions exist in a body of water and how that water's quality may be improved.


DHEC monitors surface waters to: 

  • Characterize water quality at monitoring locations (Watershed Atlas)
  • See if they are meeting water quality standards (R.61-68)
  • Identify locations in need of extra attention (303(d) List)
  • Determine long-term water quality trends
  • Provide background data for permitting, modeling, planning, and evaluating stream classifications (R.61-69) and standards (R.61-68)
  • Help formulate permit limits for wastewater discharges with the goal of maintaining State and Federal water quality standards and criteria in the receiving streams in accordance with the goals of the Federal Clean Water Act and SC Pollution Control Act.

Ambient Surface Water Monitoring

What Do We Measure and Why is it important? 

“Ambient” refers to immediate surroundings, especially pertaining to the environment around something but undisturbed or unaffected by it, as in ambient water quality.  The Ambient Surface Water Quality Monitoring Program coordinates a network of monitoring stations located across the State of South Carolina. In addition to physical parameters measured at each station, surface water samples are collected and analyzed for chemical specific parameters on a periodic basis.

There are two major components to the Ambient Surface Water Physical & Chemical Monitoring Program, including ongoing fixed-location monitoring and statewide statistical survey monitoring; each designed to provide data for water quality assessment of major water resource types at different spatial and temporal scales.
The fixed-location component of the monitoring network is comprised of Base Sites that are sampled monthly, year-round over an extended period of time, in a uniform manner to provide solid baseline data.  

Statistical Survey Sites are sampled once per month for one year and moved from year to year. The advantage of the statistical survey sampling design is that statistically valid statements about the condition of the water resources of the State can be made about large areas based on a relatively small subsample (305(b) Reports).  

Separate statistical survey monitoring schemes have been developed for streams and rivers, lakes and reservoirs, and estuarine resources to represent the entirety of each resource type. Each year a new set of approximately 30 statistical survey sites is selected for each waterbody type.  

For further information regarding Ambient Surface Water Quality Monitoring see the State of South Carolina Monitoring Strategy 2019, or water quality monitoring data, contact David Chestnut at (803) 898-4066.

Accessing DHEC Water Quality Data From The Water Quality Portal (WQP)

The Water Quality Portal (WQP) is a cooperative service sponsored by the United States Geological Survey (USGS), the Environmental Protection Agency (EPA), and the National Water Quality Monitoring Council (NWQMC). 

The STORET Warehouse was decommissioned on June 29, 2018.  WQX, the mechanism for publishing monitoring data, has remained unchanged and data continue to be available through the Water Quality Portal.

DHEC's Organization Code for Ambient Surface Water Quality Physical and Chemical Monitoring data is 21SC60WQ_WQX.

Water quality monitoring data can be selected for individual water quality monitoring sites, for all monitoring sites within a unique 8, 10, or 12-digit hydrologic (watershed) unit code (HUC), or all monitoring sites within entire counties.

The first step in the process is to identify the individual Station IDs or unique 8, 10, or 12-digit HUC, or county of the monitoring area of interest. The Station ID and water quality type will display in a popup window when using the interactive map on the Watershed Atlas

Using the unique 8, 10, or 12-digit HUC is an easy way to retrieve all of the physical and chemical water quality monitoring data within an entire watershed. Found in Nat’l Watershed Boundaries in the Watershed Atlas. Just click on the watershed of interest and copy the 8, 10, or 12-digit HUC from the pop-up box.

In general leaving Sample Media, Characteristic Group, Characteristics, and Project ID set to “All“ is the easiest way to retrieve all of the data. It is relatively easy to edit the resulting Excel file if you are only interested in specific parameters and is the most reliable way to be sure you get everything.

For more information see the Water Quality Portal User Guide

Regulatory Data and Quality Assurance Requirements

DHEC has developed a guidance document to help outside entities understand and meet the appropriate data quality requirements submitting water quality data to SCDHEC for use in regulatory decisions.

The South Carolina Estuarine and Coastal Assessment Program (SCECAP)

The South Carolina Estuarine and Coastal Assessment Program (SCECAP) is a collaborative coastal monitoring program between South Carolina Department of Natural Resources (SCDNR) and the South Carolina Department of Health and Environmental Control (SCDHEC). The goal of SCECAP is to monitor the condition of the state’s estuarine habitats and associated biological resources on an annual basis. This program significantly expands ongoing monitoring efforts by each agency and draws upon the expertise of both in a cooperative effort. SCECAP integrates measures of water quality, sediment quality and biological condition at a large number of sites throughout the state’s coastal zone. For more information and SCECAP reports, visit the SCECAP website or contact David Chestnut at (803) 898-4066.

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Water