OUTPUTS The outputs from the model include Hydrographs Flow Volume 2.1.2. SHG is defined on the basis of Albers equal-area conic map projection on. The standard hydrologic grid (SHG) is a grid system developed by USACE Hydrologic Engineering Center (HEC) to cover the conterminous United States for hydrologic modeling purpose in HEC-HMS. Standard Hydrologic Grid (SHG) and ModClark Structured Discretization In HEC-HMS.
An understanding of cascaded uncertainties from the numerical weather model through the hydrological model is necessary for a better use for forecasting. A total of six historical typhoons were used for model calibration, validation, and application. This study combines ensemble quantitative precipitation forecasts and a hydrological model to provide a 3-day reservoir inflow in the Shihmen Reservoir, Taiwan. Furthermore, being able to efficiently operate reservoirs could help maximize flood protection while saving water for drier times of the year.
The HEC-HMS interface consists of a menu bar, tool bar, and four panes. IntroductionSoftware Engineering HEC-HMS HEC-HMS 3.1.0) After a few seconds, the following should appear: Henceforth, this window will be referred to as HMS Interface. The results showed that using the ensemble precipitation forecasts with the hydrological model would have the advantage of extra lead time and serve as a valuable reference for operating reservoirs. The inflow forecasts with shorter length of cumulative time had a higher uncertainty. It found that using the ensemble-mean had less uncertainty than randomly selecting individual member.
Although Taiwan’s average annual rainfall is 2.5 times more than the world’s average, but the available rain water is only one-seventh of the world average. To mitigate the typhoon impacts, reservoirs serve as an important hydraulic structure to manage flood water release at opportune times to decrease the downstream flood risk. Typhoon-induced rainfall causes severe casualties and an annual average loss of more than 500 million US dollars. Taiwan experiences multiple typhoons annually because the island is located in the path of northwest Pacific typhoons. MoreThe available records from 1958 to 2010 show that on average 29.2 typhoons form per year, but only 3.4 affect Taiwan.
Index Flow Hec Hms Manual Of HEC
Due to non-availability of high-resolution soil maps, FAO Soil map of scale 1: 5000000 was used to generate soil related parameters.The average impact duration of a typhoon is 73.68 h in Taiwan based on 38 historical typhoon durations from 2000 to 2009. This includes large river basin water supply and flood hydrology to small urban or natural watershed runoff.Similarly, SRTM 30m DEM was used to extract topography related information using HEC GeoHMS (a geospatial extension of HEC-HMS). It is designed to be applicable in a wide range of geographic areas for solving a broad range of problems. Nevertheless, keen readers may refer toTechnical Reference Manual of HEC-HMS for more information about it.HEC-HMS is designed to simulate the precipitation-runoff processes of dendritic watershed systems. Storing reservoir inflows during a typhoon period for future uses is imperative due to limited water resources in Taiwan.The HEC-HMS user manual says the following When there are multiple subbasins above the observed flow location, a ratio can be applied to the observed flow to calculate the baseflow initial.
However, the quantity and quality of data are important for these models’ performance. Concluded that the ANN model can give good prediction performance in the long-term flow discharge to a reservoir. Other techniques, the so-called data-driven models such as artificial neural network (ANN) and autoregressive models, are also used for rainfall-runoff estimations and forecasts (e.g., ). In addition, the failure of onsite instrumentation is always a concern during an extreme event. Applying observations from rainfall gauges can provide 0 to 3 h lead time which is insufficient for reservoir operators to take preventive measures.
Wilks explained that different rainfall forecasts are not unpredictable or void of information, but rather not precisely predictable. Because of incomplete observations, approximate forecast models due to unavoidable simplifications, random errors from initial atmospheric conditions perturbing, and model parameterizations, the NWP model would generate different rainfall forecasts at the same location and time. Rainfall forecasts as input to a hydrometeorological forecast system are the main one among all sources of uncertainty. However, there are significant uncertainties associated with a hydrometeorological forecast system, including uncertainties in boundary and initial conditions and hydrological model parameters. High quality and quantity data are not easily collected and thus data-driven models are not considered in this study.As an operational system, coupling numerical weather predictions (NWP) with a hydrological model at catchment scale is a straightforward strategy to provide reservoir inflow forecasts with enough lead time.
Other than the uncertainty from NWP models, a few studies assessed the impact of uncertainty in hydrological simulations. It implied that the uncertainty of rainfall forecast is inevitable and the length of lead time is another cause. Van Steenbergen and Willems addressed that EPS can cover the uncertainty produced from the rainfall forecasts of NWP models, which is one part of the integral uncertainty. Most weather services, such as the European Centre for Medium Range Weather (ECMWF), Swedish Hydro-Meteorological Service, and US National Weather Service (NOAA), routinely use ensemble weather predictions as inputs to operational and preoperational forecasting systems. It consists of an adequate number of equally likely (equiprobable) NWP models and provides probabilistic precipitation forecasts. The ensemble predicting system (EPS), a collection of two or more NWP forecasts at the same time, is frequently used instead of a single deterministic model to capture rainfall forecasting uncertainties.
In addition, a type 3 typhoon in 2009, named Morakot, caused Taiwan huge losses. Among ten categories, type 2 has the most impact on the reservoir. Figure 1 shows that all typhoon tracks affected Taiwan according to the historical data. The Shihmen Reservoir in northern Taiwan was selected as the study area.
The dark grey polygon located in the northern Taiwan indicates the Shihmen Reservoir catchment. The percentages in the figure were the statistic results from 1958 through 2006 by the Central Weather Bureau (CWB). The integral uncertainties for magnitude and timing of peak flow and cumulative reservoir inflow were assessed and discussed.Schematic diagram of typhoon tracks invading Taiwan. All the members of TAPEX produced rainfall forecasts and the ground observations model calculated the rainfalls to reservoir inflows.
In addition, one-third of the total population of the Taipei metropolitan area, the largest one in Taiwan, is downstream. More than two million households across 27 villages and towns in three counties rely on its water supply. It has a 761.05 square kilometers (km 2) catchment area and 233 million cubic meters (m 3) of effective storage capacity, which ranks the first and third among all reservoirs in Taiwan, respectively. The Shihmen Reservoir is a multiple-purpose reservoir, including irrigation, water supply, flood control, hydropower, and recreation. Study AreaThe Shihmen Reservoir catchment, located at the upstream of the Tanshui River in northern Taiwan, was selected as the study area (Figure 2).
Taiwan Cooperative Precipitation Ensemble Forecast Experiment (TAPEX)TAPEX, a collective effort among academic institutes and government agencies, such as National Taiwan University, National Central University, National Taiwan Normal University, Chinese Culture University, Central Weather Bureau (CWB), National Center for High-Performance Computing, Taiwan Typhoon and Flood Research Institute, and National Science and Technology Center for Disaster Reduction, started in 2010 and is the first attempt to design a high-resolution numerical ensemble model in Taiwan. To achieve these two goals of water supply and flood mitigation at the same time, the operator must be precise when releasing flood waters.Flow chart of this study in terms of data processing and performance evaluation. Therefore, flood control through reservoir operations is very important for downstream flood mitigation during typhoons. Mentioned that the vulnerability to 200-year flooding still exists due to urban development and natural alteration over time.
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