WSPC01928 - Laserfiche WebLink

Home Browse Search

'1'2'01'4 Introduction Summary The following sections describe major components of HYDROSS and how they are used. 1.4.1 Demands: HYDROSS recognizes four kinds of demands for water; instream flow requirements (IFRs), power requirements (PWR), diversion requirements (DIY) and storage requirements. An instream flow requirement is a demand that requires a given flow to be maintained in the system at a given location. The instream flow requirement can vary both monthly and yearly. Water required by an instream flow requirement is not withdrawn from the stream and is available for use downstream of the flow requirement. A Dower reouirement is a demand which occurs at a reservoir and can vary monthly and yearly. The flow required to satisfy the power demand is . calculated based upon reservoir content (head), tailwater, and efficiency data. A diversion reauirement ta1ces water from the system and potentially denies the water from other users with a later water right date. A thorough discussion of diversion requirements is presented in the diversion section of this document. A storal!e reauirement is used to fill reservoirs and is satisfied only after the other three types of requirements are satisfied. 1.4.2 Natural and Proiect Flow: HYDROSS recognizes and allocates two "types" of water; natural flow and project flow. Natural flow is the flow that would occur in the system in the absence of any "man-related" effects. Proiect flow is water which has been stored or otherwise appropriated as project water. 1.4.3 Water Ril!hts: Natural flows are first used to satisfy natural water rights. If all natural rights have been satisfied then natural flow can be used to satisfy project water rights. If all natural and project rights are satisfied, natural flow may then be stored. Project water is used satisfy project rights when natural flow can not. Project water can not be withdrawn to satisfy a natural right. HYDROSS allows the user to assign priority dates for diversions, instream flows, and power generation. A 4-digit code is used to establish the priority scheme; where 0001 would be the highest priority and 9999 the lowest. HYDROSS does not allow the user to assign a priority date to a reservoir for storage, this is automatically assigned a priority of 9999. However, a reservoir with priority dates can be modeled with priority dates using a diversion to deliver water to the reservoir (see section 5 [page 29]). 1.4.4 Reservoir Ooerations: The HYDROSS model uses five decision levels (based on content) in the operation of reservoirs; the absolute maximum, maximum, target, minimum, and absolute minimum. The absolute maximum and absolute minimum are fixed values based upon physical limitations of the dam and outlet works. The maximum and minimum are limits which can vary both month to month and yearly and allow the user to simulate reservoir operations by drawing a reservoir down to or not allowing the reservoir to drop below a specified content. HYDROSS will not willingly retain or release water in a reservoir beyond the these limits. The tarl!et level is used in the pool maintenance routine among multiple reservoirs and at offstream storage sites. 1.4.5 Pool Maintenance: This routine (if switched on) will attempt to balance reservoir storage in a system of reservoirs by releasing water from upstream reservoirs to bring all reservoirs under consideration to the same index level (see section 5 [page 29]). HYDROSS also allows the user to call for release of stored water, for project demands, from specific reservoirs in a specified sequence. Using specified reservoirs for release along with variable maximum, minimum, and target levels, provides the user with the flexibility to make the river system operate the way he/she wants it to. 1.4.6 Discharl!e Caoacity and Seeoal!e: HYDROSS allows the user to specify a table of maximum outlet works discharge capacities in which discharge is a function of content. Page 2 HYDROSS 4.1 March 25, 1991