Agenda - 11-19-1985 - Laserfiche WebLink

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, . ■ + ' 3 area for which run-off may be captured) , based upon present _ operating practices, is at times as low as 27.77 square L miles. 'These practices (i.e. having to keep the augmented - . water supply at dam level in order to pass water to Ben Johnson) prevent the reservoir from capturing the full runoff . 1 = from its drainage area. The same condition has existed to a c - lesser extent at Lake Ben Johnson where the shallow depth of the intake and reluctance to use the release structure • prevent full use of storage. , . Thirdly, while the Upper Eno River Basin is relatively . small the distribution area is considerable. Orange Alamance serves customers in two counties and two major basins (Neuse ' and Cape Fear) . By the same token Hillsborough's water sales to CATA$A have resulted in water distribution and ultimate loss tolanother basin. - 1 t - III. % . DIN Tp BE ANSWERED AND DEFINITIONS [ . ' 1 What is the capability of the Upper Eno River with its reservoirs to accommodate water withdrawal and instream flow protection demands? Stated in other terms, to what extent is the river at capacity given the withdrawals being made? If . e capability is low or under capacity use conditions what should be done about it? By "water withdrawal" it is meant to refer to the rates of water removed from the river for purpose S of treatment and sale (wholesale and retail) . "instrebm flow requirement" is the term given to a variety of •governmental measures designed to maintain certain minimum flows in rivers and streams. These measures take the form of - - requirements to ensure water quality, sustain fish life and preserve habitat fer fish or game. The concept of maintaining a minimum flow release from water sppply impoundments dates from about 1960. Laws to implement the concept were passed in 1967. Recent projects in the 'triangle area, including the Little River Dam and the Eno River withdrawals for the City of Durham and the tempordry and permanent impoundments on Cane Creek for GWASA have each been assessed with a prescribed minimum flow release incorporated into one or more of the various permits for construction. The proposal by the State NRCD Division of Water Resources to establish a minimum instream flow require- ments en the Eno River below Lake Ben Johnson is preceeded by • such action involving the City Lake at Rocky Mount. As related to Orange County the State is a downstream reparian owner With the presence of the Eno River State Park in Orange County 1 rv. METH Iwo , . In seeking to answer the first study question the Division of Water Resources used what it called the Recursive Simulation Computer Model to the analyze the River as it is currently operated. At the County's request it took into account different withdrawal rates as might be applied assuming water use restrictions during danger periods and various factorings for instream flow protection. measurement of river flows was based on data recorded over a 40 year 1