2010年-世界发展银行全球_Economics_of_Adaptation_to_Climate_Change__Ethiopia_Volume_2_Annexes_41页_3mb

报告摘要

Summary of the Document

Core Content

This document provides an overview of two hydrological and agricultural models used to assess the impact of climate change on water resources and crop yields in Ethiopia. It includes detailed descriptions of the CLIRUN-II rainfall-runoff model and the CliCrop crop model, along with their applications and methodologies.

CLIRUN-II Rainfall-Runoff Model

Background

CLIRUN-II is a hydrological model designed to analyze the impact of climate change on runoff, particularly for extreme events.
It is part of the "Kaczmarek School" of hydrological models and incorporates features from both CLIRUN and WATBAL.
CLIRUN-II uses a two-layer approach to simulate soil and groundwater interactions.

Key Features

Spatial and Temporal Scale: Simulates runoff at a gauged location, using monthly climate and runoff data.
Snow-Balance Model: Uses monthly temperature and precipitation to calculate effective precipitation, which includes snowmelt.
Water Balance: Models the inflow and outflow of water, accounting for storage changes in soil and groundwater.
Soil Water Modeling: Consists of two layers (soil and groundwater), with nonlinear equations to determine percolation and runoff.
Model Calibration: Enhanced to account for dry, normal, and wet years, improving the R² value from 0.7 to 0.92.
Runoff Results: The document includes time series of annual streamflow changes for the Gibe Omo and Blue Nile basins under four climate projections.

CliCrop Model

Background

CliCrop is a crop model developed to address specific challenges, such as modeling zai holes and mulching and estimating the impact of climate change on crop yields.
It is based on CROPWAT but includes additional features for more accurate yield estimation.

Key Features

Input Requirements: Designed for large-scale yield calculations, using historical and future weather data, and soil data.
Precipitation: Requires daily precipitation data in millimeters per day.
Potential Evapotranspiration (PET): Estimated using the modified Hargreaves equation, based on daily temperature, temperature range, and latitude.
Crop Parameters: Includes single crop coefficients (Kc), basal crop coefficients (Kcb), crop stage durations, and yield coefficients.
Soil Properties: Uses hydraulic conductivity, wilting point, field capacity, and saturation. These are estimated based on location using data from FAO Soil Map of the World and NCAR methods.
Water Transport: Simulates soil moisture movement using equations from SWAT, including percolation and upward flow.
Ponding and Deep Percolation: Models the loss of water due to ponding when soil moisture exceeds saturation and deep percolation beyond the semi-impervious layer.
Water Table: Used to assess waterlogging losses, measured from the bottom soil layer to the furthest saturated layer.

Yield Calculations

Yield is calculated based on the ratio of actual to potential evapotranspiration.
Five yield values are computed: one for each of the four development stages and one for the entire growing season.
The lowest yield among the five is considered the true yield.
The yield coefficient (Ky) is used to estimate the impact of water stress on yield.

Key Information

CLIRUN-II improves upon earlier models by focusing on extreme events and incorporating a two-layer system.
CliCrop is designed to provide insights into agricultural techniques that could mitigate climate change impacts on crop yields.
The models use empirical and theoretical methods to simulate water and crop interactions.
Soil and climate data are essential inputs for accurate modeling.
The document includes figures illustrating the conceptual models and processes used in both CLIRUN-II and CliCrop.

Conclusion

The CLIRUN-II and CliCrop models are essential tools for understanding the effects of climate change on water resources and crop yields in Ethiopia.
These models offer improved accuracy and flexibility in simulating both hydrological and agricultural processes.
They support policy and agricultural decision-making by providing insights into yield changes and water management strategies.