The Impact of Water Transfer among Sectors on Regional Drought Risk Distribution

• Main Authors: Tzai-Hung Wen, 溫在弘
• Other Authors: 蘇明道
• Format: Others
• Language: zh-TW
• Published: 2006
• Online Access: http://ndltd.ncl.edu.tw/handle/57340618363402321866

博士 === 國立臺灣大學 === 生物環境系統工程學研究所 === 94 === The droughts often result from inadequate precipitation for meeting the water demands. The increase of water demands makes drought a more frequent phenomenon. Due to the low economic efficiency of agriculture activities as well as political and national economy concerns, irrigation water supplies are usually regarded as temporary water reallocation sources available for supporting municipal and industrial (M&I) activities during severe droughts. The purpose of the study is to evaluate the impacts of different water transfer strategies among sectors on regional drought risk distribution. A comprehensive framework of risk analysis for natural hazards is used in this study, including potential hazard analysis, vulnerability assessment, and risk management instruments. Drought vulnerability is defined as the product of the vulnerability weight and water deficit. The weight reflects f the economic impacts of suffering droughts in spatial, temporal, and sectoral dimensions. A geographic information system (GIS) is used to capture spatial variations of human activities, including irrigation and M&I sectors in order to estimate regional water demands and establish spatial relationship between demand sites and supply infrastructures. The study area located in southern Taiwan incorporates 8 surface and 2 underground water supplies, 8 reservoirs and 629 demand sites, including 570 irrigated areas and 59 M&I areas in ChiaNan area. A mixed integer linear programming (MILP) model with minimizing regional drought vulnerability as the objective is established for inter-sectoral drought allocation. Exceeding probability curves and spatial mapping of drought risk are established under different water transfer scenarios, including inhibition of water transfer among sectors (scenario 1), and transfer criteria based on specific amount of agricultural water (scenario 2) and priority of economic-efficiency (scenario 3). The results show that average deficit rate is about 14.8% for irrigation, 8.6% for M&I under scenario 1. Under this scenario, higher drought risk in irrigated areas appears in the areas with rotated paddy crop and area with sugarcane. The M&I sectors suffer from higher risk more in the mountainous and coastal regions. In scenario 2, transferring about 20% of the irrigation water can reduce the drought risk for M&I sector in coastal areas. It is also shown from the simulation when the transfer rate is more than 40%, no further benefits are shown for retarding M&I drought risk. Comparing scenario 3 with scenario 1, it could be found that average deficit rate of M&I sectors reduced from 8.6 % to 1.2 %, and that of agricultural sector increased from 14.8% to 23%. M&I drought vulnerability reduced substantially from 43,814 thousands to 7,030 thousands NT dollars (83.9%), and the agricultural sector increased from 23,644 thousands to 30,048 thousands NT dollars (27.1%). The results of this study show that the water transfer strategy based on economic-efficiency consideration (scenario 3) could reduce about 60% M&I drought vulnerability in ChiaNan region. The compensation for paddy-farming fallow from the M&I sectors should reflect this contributions accordingly rather than merely the actual farming loses. However, the results also show that the M&I sectors tend to reduce water demands if their marginal benefits for water consumptions are less than $22/ton. And the M&I drought vulnerability will be even larger than the agricultural sector if marginal benefits for M&I sector decrease less than $18/ton. This study shows that the compensation of $6-8/ton for fallow of paddy-farming is reasonable for water transfer to M&I sector.