Orange County NC Website
Browse       Search
Attachment 2. (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 1 -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 />