Spatial Analysis for Impact of Fallow Decision on Regional Irrigation Demand
Date Issued
2006
Date
2006
Author(s)
Wang, Shih-Fu
DOI
zh-TW
Abstract
Although with abundant annual precipitation, Taiwan suffers from frequent drought due to the in-uniform rainfall distributions in temporal and spatial aspects. Due to the large share of water use for agriculture sector, fallow becomes an important measure for water shortage mitigation during the drought. It is also a mean to reduce the rice production in response to the produces imports since Taiwan’s participation to the WTO in 2002. It can be anticipated that fallow may become more frequent phenomena and important concerns in the future regional water resource management. Experiences for prioritizing the fallow sequences during the drought have been learnt from past researches, but the irrigation demand reductions from different fallow decisions are not readily available. This study therefore aims to discuss the impact of fallow decision on regional irrigation demand through spatial distribution consideration of the fallow farms.
The command area of Chia-Nan Irrigation Association in southern Taiwan was chosen as the study area. A simulation model was built for irrigation demand estimation under scenarios of different cropping patterns including fallow. The irrigation group, with an area of about 150 hectares, is used as the basic decision unit. There are more than 650 irrigation groups in Chia Nan Irrigation Association. Each irrigation group is assigned with an attributes as the distance to the water supply source. Irrigation groups are also assigned an index showing its spatial grouping relation according to distribution canal systems. System simulation is done with the model to study the variations of irrigation demands with the spatial pattern of fallow paddy farms. The concept of spatial autocorrelation is used to establish an index for evaluating the effectiveness of irrigation demand reduction under different fallow strategies.
The results show that the variations of irrigation are largest, as much as 14.7%, for different spatial fallow patterns when the fallow area is about 50%. When the fallow regions are farther away from the water supply source and are more aggregated together, the smaller the irrigation demands are. It is concluded that more water can be saved from the same fallow area if the fallow decisions are planned carefully. The proposed evaluation index for effectiveness of irrigation demand reduction can be used for evaluation of different fallow strategies at the planning stage and to improve the regional water management effectiveness.
Subjects
休耕
節水效率
輸水損失
Fallow
Water Use Efficiency
Conveyance Loss
Agricultural Water Demand
SDGs
Type
thesis