Planning for Reuse – A Brief Look at Long-Term Water Availability in NC
By A. Robert Rubin, Ed. D, Senior Environmental Consultant, McKim & Creed

The nexus of weather, climate, population pressures and resource availability will dramatically influence resource management in North Carolina and the Southeast. What influence will this nexus have on water resource management and water reuse programs? The drought is over – right? But how will future water emergencies impact water management in North Carolina and the Southeast?

Demographers project that the population of North Carolina will increase by 25 to 30 percent by 2025. In addition, industrial growth and development, recreation, and agriculture will continue to exert demands on available water resources. North Carolina and other states along the eastern seaboard are unique; our watersheds begin in the Appalachian Mountains and generally flow eastward to the Atlantic. These watersheds are small when compared to the watersheds in the western states. There is a perception of plentiful water, but the supply has been strained for the last few years, and the increasing pressures on the current levels will only exacerbate resource management challenges. Water reuse can play a major role in allocation of water resources in the Southeast.

Water resource managers from the Southeast meet annually to address demand issues and management strategies. In recent years, a portion of the program has been devoted to issues of reuse. The importance of reuse was codified in North Carolina with passage of the Drought Management Bill in 2008 (2008-1943). This bill establishes requirements for any entity withdrawing or transferring over 100,000 GPD from surface or groundwater sources, and it also assigns responsibility to North Carolina Department of Agriculture to initiate a survey of all agricultural, silvicultural, and horticultural users withdrawing 10,000 GPD or more from any source. Section 143-355.5 of the bill contains provisions for reuse. The bill states that reuse is critical to meet existing and future water demands in North Carolina. We have a mandate to reuse reclaimed water; consequently, a responsibility to do that wisely. This bill is an important tool to help communities plan for reuse and wise water management.

Planning for reuse will require that communities assess potential demand. This can be done by examining water users in the community and identifying activities amenable to reuse. Planners can incorporate access to water reuse pipelines as a tool in land use decisions. Activities such as residential toilet flushing, fire protection, heating and cooling water, irrigation, aesthetic uses, ecosystem enhancements and dust control can all be accomplished with reclaimed water. Effective planning must incorporate reuse into local decisions.

The need to assess reuse is projected often by the Drought Management Advisory Council website (ncdrought.org). Prominent on this site is a frequently updated drought severity index. This site demonstrates that until December 2009, half the counties in North Carolina were considered abnormally dry or in moderate drought. Since 2002, the state has experienced two severe droughts, (i.e., droughts with severity index values over 4). This information is an important tool to help communities plan for reuse.

North Carolina rules now incorporate standards for reclaimed water quality and treatment system design. Water quality standards can vary depending on the intended use of the reclaimed water. Regardless of the intended use, water quality standards are stringent. The most stringent standards are associated with reuse activities that may expose residents of a community to reclaimed water. Golf courses or athletic field irrigation, toilet flushing or wetland augmentation require stringent limits. Crop irrigation where plant materials are not intended for direct human consumption requires less stringent standards. The risk determines the treatment levels required.

Crops such as turf (grasses) can be viewed as supporting direct contact; when used as grasses on a golf course, turf crops support recreation. When viewed as a grow-out for high-value turf for the golf course or the athletic field, the same grasses are an agricultural commodity. If reclaimed water is used in support of recreation, high standards must be imposed to protect public health. If the grow-out operation receives reclaimed water, the stringent reuse standard may not apply.

Agricultural and horticultural crop irrigation in North Carolina covers almost 250,000 acres (USDA Census of Agriculture, 2009). Assuming the crop irrigation is intended to satisfy a deficit in evapotranspiration, a liquid loading of about 15 inches per acre is required. If the crop is a high-value turf system, liquid loadings may increase to 25 inches per year. For purposes of this discussion, assume a liquid load of 15 inches per acre in a growing season. The volume of irrigation water required to satisfy this demand is almost 4 million acre inches, which is equivalent to over 90 billion of gallons of water used in agriculture. Interestingly, the majority of farms employing irrigation typically contain 10 irrigated acres, and the 3,000 small farms in this range could consume over a billion gallons of water annually. This demand could be supplied by reclaimed water.

Demand management is a critical next step in the planning-for-reuse effort. Once potential demands have been identified, reclaimed water generators must assess the supply issues associated with meeting the demands. This requires assessment of seasonal needs and volumes. The pumping systems, line sizes, and storage requirements necessary to support reuse must be assessed in this phase of a reuse effort. Competing demands for available water are already creating allocation issues throughout the region. Changing weather and rainfall patterns may exacerbate already sensitive allocation issues.

What do implications associated with changing rainfall patterns hold for North Carolinians? Climatologists tell us that the annual volume of rainfall may not change markedly, but the distribution of that rainfall will. Short and intense rainfall events are likely. The volume of water that can enter the complex aquifer systems may be reduced. This reduces the volume of water available to well systems and potentially to surface streams. Supplying the demand for water will become increasingly difficult, and reclaimed water programs will play an increasingly critical role in water resource management programs vital to the state. Effective water reuse program planning must begin now. The Drought Management Bill is a prescient indicator of our future.

Crop irrigation where plant materials are not intended for direct human consumption requires less stringent standards.

Activities such as residential toilet flushing, fire protection, heating and cooling water, irrigation, aesthetic uses, ecosystem enhancements and dust control can all be accomplished with reclaimed water.

There is a perception of plentiful water, but the supply has been strained for the last few years and the increasing pressures on the current levels will only exacerbate resource management challenges. (Photo by Jerry Blow Architectural Photography)

Water reuse can play a major role in allocation of water resources in the Southeast. (Photo by Jerry Blow Architectural Photography)