Orange County NC Website
Browse       Search
8 <br /> Attachment B. Continued <br /> Modeling Data Gaps <br /> UNRBA re-modeling of Falls Lake is expected to start in approximately 2 years, and is intended <br /> to update the lake response model that DWQ utilized in the development of the Falls Lake <br /> Rules. The UNRBA contractor identified several gaps in the data used by DWQ in the modeling <br /> completed during the development of the Falls Lake Rules, including: <br /> • DWQ held constant the total organic carbon and chlorophyll-a input values assumed for <br /> the tributaries feeding into Falls Lake. These concentrations were based on levels <br /> measured within the lake, not in the tributaries. It is probable that these concentrations <br /> were artificially high to begin with and were unable to decrease at all over the course of <br /> the modeling study. <br /> • There are no stream gages on any of the streams that flow into Falls Lake east of I-85, <br /> thus no flow information was incorporated for any of these 12 streams. <br /> • Atmospheric deposition of nitrogen in the lake or watershed was not accounted for by <br /> DWQ. <br /> • Streambank erosion, possibly a significant source of phosphorus in the watershed, was <br /> not considered as a possible source by DWQ. <br /> • Internal lake processes, such as sediment re-suspension, were also not accounted for by <br /> DWQ. <br />