Calvin Sawyer

The South Carolina Digital Watershed: End-to-End Support for Real-Time Management of Water Resources

Water resources are under unprecedented strain. The combined effects of population growth, climate change, and rural industrialization have led to greater demand for an increasingly scarce resource. Ensuring that communities have adequate access to water—an essential requirement for community health and prosperity—requires finegrained management policies based on real-time in situ data, both environmental and hydrological. To address this requirement at the state level, we have developed the South Carolina Digital Watershed, an end-to-end system for monitoring water resources. In this paper, we describe the design and implementation of the core system components: (i) in situ sensing hardware, (ii) collection and uplink facilities, (iii) data streaming middleware, and (iv) back-end repository and presentation services. We conclude by discussing key organizational and technical challenges encountered during the development process.

Eroded Particle Size Distributions for Southeastern U.S. Soils

Sediment is a significant negative byproduct of construction sites, agriculture, mining, and other land disturbing operations. Recently renewed attention has been given to controlling construction-derived sediment loading to natural waters. Evaluation of sediment control systems usually involves models that require input for prediction of sediment transport and deposition; therefore it is important to obtain eroded size distributions (ESD). ESD is used in detachment equations and determining pond efficiencies. Currently recommended procedures for estimating eroded size distributions used in design of sediment control structures often revert to simplistic rule of thumb methods, primarily due to lack of a universally accepted method. Sediment ponds and other structures designed by such estimates may be oversized or undersized. Another recommended method is based upon equations to determine amounts of sand, silt, clay, and large and small aggregates. Percentages of each are then used to estimate an ESD. Much research has been done for primary particle size distributions. The basic process is to take a sample of soil and mix a solution of sodium hexamedaphosphate and water to disperse aggregates into primary particles. However, primary particle distributions are not what are needed for estimating sediment transport and deposition because aggregates are naturally present in sediment-laden runoff. The importance of ESD becomes evident in settling velocities and in the amount of force required to keep the particle in transport. Previously, equations were statistically produced from a limited number of soils and later improved to better predict the amount of eroded material. These equations are used in the CREAMS (Chemical, Runoff, and Erosion from Agricultural Management Systems) and other models. However, these equations have limited applicability because they were developed for agricultural soils with high clay content and organic matter. This paper compares methods based on the CREAMS equations with ESD obtained from a rainfall simulator in predicting ESD from soil textures in 17 southeastern U.S. topsoils and subsoils. Additionally, USDA Natural Resources Conservation Service soil surveys contain dispersed particle size data in the engineering section. These data were used to get average percent clay and sand as input for the CREAMS equations, and values are then interpolated for ESD. A standard hydrometer test was also performed on each soil sampled in this project. ESD was calculated in much the same way as the soil surveys, except texture is a direct result of the hydrometer test. In addition, impact of errors in eroded size distribution on trapping efficiency of sediment control structures will also be demonstrated.

Analysis of Escherichia coli within Sediment Basins on Active Construction Sites

The conventional method of controlling sediment-laden runoff on construction sites is the use of sediment basins. These basins slow the velocity of runoff and allow particles to settle from the water column before discharge to surface waters offsite. This best management practice, however, may create a reservoir for Escherichia coli. Sediment is known to provide protection for bacteria; therefore, while these basins decrease sediment loadings to water bodies downstream, they may introduce harmful levels of pathogenic bacteria into receiving waters. In addition to increasing risk to human health, high bacteria levels may alter natural biological complexity of downstream ecosystems.

Accuracy and Precision of Portable Turbidity Meters

EPA has published effluent limitations guidelines (ELGs) to control discharge of pollutants from construction sites. Numeric turbidity limits for construction site discharge are expected to be required in the near future. Such requirements will likely include subjecting construction site stormwater discharges to a maximum allowable turbidity numeric effluent limit in nephelometric turbidity units (NTUs) for sites disturbing 10 acres or more

Developing Stormwater Educational Programs for Rapidly Urbanizing Areas

Like many areas throughout the U.S., urban growth within South Carolina is occurring at a tremendous rate. As a result of environmental concerns, the Clemson University Cooperative Extension Service initiated public education programs in communities across the state. This presentation provides details about how Clemson became involved, as well as Extension’s role in implementing programs in local communities having diverse needs. The presentation describes development along with many other issues involved with developing and funding long term programs that meet regulatory requirements.