Daily Time Step Simulation with a Priority Order Based Surface Water Allocation Model
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Date
2011-02-22
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Abstract
Surface water availability models often use monthly simulation time
steps for reasons of data availability, model parameter parsimony, and reduced
computational time. Representing realistic streamflow variability, however,
requires modeling time steps with sub-monthly or daily temporal resolution.
Adding daily time step simulation capability to the Water Rights Analysis
Package (WRAP) and the Texas Water Availability Modeling (WAM) System is
a growing area of need and interest in water rights permitting, water supply
planning, and environmental protection.
This research consisted of the following tasks:
1. Key modeling issues are identified that are relevant to daily time step
modeling, but are otherwise not considered with monthly
simulations. These key modeling issues include disaggregating
monthly naturalized flows into daily flows, routing changes to flow
through the stream network, reducing impacts to water availability in
a priority order based water right system through the use of
streamflow forecasting, distributing water right targets from monthly to daily amounts, and integrating flood control reservoir operations
into the existing conservation reservoir modeling framework.
2. Two new programs for WRAP are developed to address the key daily
time step modeling issues. The new programs include a pre-processor
program, DAY, and a daily simulation program, SIMD.
3. A case study of the Brazos River Basin WAM is presented using daily
time steps with SIMD. The purpose of the case study is to present an
implementation of the daily modeling capabilities.
4. The case study simulation results are used as a basis to draw
conclusions regarding monthly versus daily simulation outcomes.
The research, as presented through the Brazos River Basin WAM case
study, illustrated that incorporating realistic daily streamflow variability into
the simulation of a priority order based water allocation system can
substantially affect the results obtained for time series of critical period reservoir
storage contents, the determination of long-term water right reliability, and the
distribution of unappropriated and regulated flows. The modeling capabilities
developed by this research advance the state of water availability modeling with
sub-monthly time steps by addressing the key modeling issues related to
streamflow variability and routing.
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Keywords
water availability, prior appropriation, water right, reservoir, simulation, time step, monthly, daily