ORD-2010-025 Upper Eno Watershed Critical Area-Zoning Ordinance

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Attachment 4 25 WATER SUPPLY WATERSHED PROTECTION IN ORANGE COUNTY Teny Hackett, Stormwater Resource Officer Erosion Control Division -Orange County Planning and Inspections January 2010 Introduction Orange County is often referred to as a "headwater county, meaning the county is located at the upper end of larger watersheds or river basins. Most streams actually originate in the county rather starting elsewhere and simply flow through. This is an important distinction because of the designated water supply reservoirs located downstream. Equally important are the water supply reservoirs located within the county. For these reasons protecting water quality has been an important aspect in planning development and land use within Orange County. Headwater Streams and Watershed Health Research suggests that headwater streams play a critical role in the overall health of watersheds. Headwater areas influence the supply, transport and quality of water downstream (Alexander, et al., 2007). Many natural biological, chemical and microbial processes occur in these headwater streams, making them vulnerable to land use changes. Research suggests that protecting these areas are vital in maintaining downstream water quality and aquatic ecosystem health. Headwater streams are critical for maintaining ecological health and biodiversity of watersheds (Doppelt, et al., 1993). In Orange County, this is even more significant because our watersheds are relatively small and the streams draining them become critical elements in protecting water quality within the watershed. Need for Protecting Larger Streams Protecting small first and second order headwater streams is only one aspect of a successful watershed protection program. Protecting larger, perennial streams such as third, fourth, and fifth order streams is also necessary. Higher order streams are typically perennial and contain higher flow. Perennial stream flow often equates to higher diversity in aquatic species, especially fish, mussels and crustacean species. Greater species diversity relates to better stream health and provides recreational opportunities, such as fishing. Larger streams can be more susceptible. to spills and other pollutants. Studies indicate that larger streams have fewer biological, chemical and microbial processes occurring compared to first order streams. Thus, larger streams have less ability to remove or reduce a pollutant before transporting it downstream through higher stream flow. For instance, a chemical spill in a headwater stream, while bad for the environment, typically has a greater chance that natural processes can conceivably reduce the impact when compared'to a spill that reaches a higher order stream with higher stream flow. Higher stream flow equates to faster transport rates of the pollutant, which in turn increases the likelihood of that pollutant reaching a downstream water supply reservoir. For these reasons, the state of North Carolina requires protection zones upstream of surface water intakes. There are two basic zones, a "critical area" and "watershed protection area°. Critical areas are designated 'h mile upstream of an intake and include both water and land. Critical areas are given more stringent protection since there may be limited time for a water plant operator to react to a spill and shut down the intake. Beyond the critical areas are Page 1 of 3