2015年-世界发展银行全球_Water_and_Climate_Adaptation_Plan_for_the_Sava_River_Basin___Annex_1_Development_of_the_Hydrologic_Model_for_the_Sava_River_Basin_100页_4mb

Summary of the Water & Climate Adaptation Plan for the Sava River Basin - Annex 1

Core Content

This document outlines the development of a hydrologic model for the Sava River Basin (SRB) as part of the Water and Climate Adaptation Plan (WATCAP). The model is designed to simulate the hydrologic regime of the SRB on a 10-day or monthly time scale, enabling the assessment of the basin's response to future climate scenarios. The model development is based on data collected from meteorological and hydrological stations, as well as digital elevation models (DEMs), and is primarily conducted using the HEC-HMS software.

Main Objectives

• To develop a hydrologic model for the SRB that can be used for climate change impact analysis.
• To simulate hydrologic responses under different climate scenarios.
• To provide a basis for decision-making in water management sectors such as navigation, hydropower, flood control, and irrigation.

Key Components

1. Model Selection

• The HEC-HMS model was selected as the platform for hydrologic simulation due to its availability, low data requirements, and compatibility with the needs of the project.
• The model was initially developed by the USACE for flood hydrograph estimation but was not suitable for continuous simulation due to its event-based nature and lack of features such as interception and snow melt.
• A new model was developed based on continuous meteorological and hydrological data.

2. Data Collection

• The primary input data includes: daily precipitation, daily air temperatures, and monthly potential evapotranspiration.
• Hydrological data (daily flows) is also required for calibration and verification.
• Data was collected from:
  • The World Bank's previous work on the Sava Basin.
  • Five riparian experts who gathered data from selected stations.
  • Additional data from the Vrbas Study project and the Hydro-meteorological service of Montenegro.
• Due to data gaps, especially in Croatia and Bosnia and Herzegovina between 1991 and 2005, a regional climate model (NHMM) was used to reconstruct missing data for the period 1961–1990.

3. Basin Subdivision

• The SRB was divided into two levels of sub-basins:
  • First Level: 14 major sub-basins, including the upper Sava in Slovenia and its major tributaries.
  • Second Level: 44 sub-basins, with 35 controlled by hydrologic stations at the outlet.
• Sub-basin boundaries were manually adjusted in certain areas where automatic delineation was inaccurate, especially in the plains of the Sava River valley.

4. Calibration and Verification

• Two 5-year periods were selected for calibration and verification:
  • Calibration: October 1979 to September 1984
  • Verification: October 1969 to September 1974
• These periods were chosen to ensure data availability and representativeness.
• Model performance was evaluated using metrics such as the Nash-Sutcliffe Efficiency (NSE) and Percent Bias (PBIAS).

5. Climate Scenarios

• Future climate scenarios were incorporated into the model by using outputs from five Global Climate Models (GCMs) and Regional Climate Models (RCMs).
• The model was run with both baseline and future climate scenarios to assess changes in seasonal and annual runoff, as well as high and low flow conditions.
• Results showed variations in runoff across different sub-basins, with ensemble median values used to summarize trends.

6. Uncertainty and Limitations

• The model's accuracy was affected by data gaps and the limitations of the NHMM in mountainous areas such as the upper Drina basin.
• Despite these uncertainties, the model was found to be sufficiently accurate for the purposes of the WATCAP project.

Key Information

• Basin Area: Approximately 96,400 km²
• Total Length of Sava River: 990 km
• Average Discharge at Belgrade: 1700 m³/s
• Average Runoff Yield: 18 L/s/km²
• Calibration Period: 1979–1984
• Verification Period: 1969–1974
• Model Software: HEC-HMS
• Time Step: 12 hours (initially 1 day)
• Data Sources: World Bank, riparian experts, meteorological services, and regional climate models.

Main Viewpoints

• The HEC-HMS model was adapted for continuous simulation to meet the needs of climate change analysis.
• The model's performance was validated against observed data, with acceptable results.
• The use of climate models to simulate future scenarios is essential for understanding potential impacts on water resources.
• Data availability and quality were critical factors in model development, particularly for the period 1961–1990.
• Manual adjustments were necessary in certain areas due to the limitations of automated delineation methods.

Conclusion

The development of the hydrologic model for the Sava River Basin represents a significant step in the WATCAP project. It enables the assessment of climate change impacts on water management and provides a tool for future planning and adaptation. The model is based on continuous data and calibrated against historical records, with results indicating the potential changes in runoff and flow conditions under future climate scenarios.