An Efficient Irrigation Water Distribution Model in Water Short Environment
Date Issued
2004
Date
2004
Author(s)
Chen, Ching-Tien
DOI
zh-TW
Abstract
The main purpose of irrigation is to provide enough water to maintain normal crop growth and further to assure the agricultural production. Due to the effect of topography and geography, and unbalanced distribution of rainfall on space and time, the shortage of available water resources has been common in Taiwan. Thus, the implementation of irrigation plan management in each Irrigation Association of Taiwan is based on the irrigation rate on the water source supply basis. This method is convenient to carry out but under the restriction of water source quantity, still unable to satisfy the water demand for crop growth and indeed would affect the sustainable use of water and soil resources in the long term. The current trend in irrigation requirement is based on field crop irrigation requirement and coordinated with current irrigation system in Irrigation Association to construct a demand-oriented irrigation requirement estimation model and a balanced irrigation water redeployment model, which is also the emergent duty for agricultural water resource planning scholars.
Under the recent influence of entering WTO and greenhouse effect, the agricultural production structure and water resource amount distribution in Taiwan would change in the future. It is urgent and essential for researchers to assure the crop irrigation demand in each growth stage, through effective irrigation redeployment management, and further to enhance both agricultural production and sustainable use of field. Crop variety has become a trend in maintaining competitiveness of agricultural productivity. However, as the mixture of crops in field becomes significant, the distribution of irrigation water becomes more difficult as well. As a result, the establishment of a water distribution model capable of satisfying the water requirement of mixed-crops in field has become an important issue.
In this research, data such as climate record, soil texture, effective rainfall, irrigation area and crop types were collected to construct a irrigation requirement estimation model for area of mixed cultivation, which satisfies various crop growth demands, to quickly and precisely estimate irrigation requirement for area of mixed cultivation in paddy rice and upland crops and further to analyze fair irrigation demands at each Irrigation Association in Taiwan for further application of irrigation redeployment plans. Next, to optimize the water resource during water shortage period, the maximum irrigation interval of crops, with agricultural production conditions unaffected, during important growth stages, such as the tillering stage, the panicle differentiation stage etc., were analyzed with pot experiment in this research for application of irrigation redeployment models. Lastly, the water distribution efficiencies of modified K-factor and the original K-factor at main and lateral canals were compared under the condition of balanced when farm water supply and demand, in which farm areas, canal and ditch lengths, and crop types are considered, to conduct and verify with on-site data to establish a mobile water distribution model which assure both various crop irrigation demand and variant water resources to solve the irrigation water distribution problems for area of mixed cultivation.
The results of research, from the analysis of current irrigation water data at each Irrigation Association in Taiwan, reveal that the theoretical planned irrigation water amount, which assured normal crop growth, was more than planned irrigation water amount and actual intake water amount with the same planned irrigation area, especially among those with larger irrigation areas including Chia-Nan, Yu-Lin, Chang-Huwa Irrigation Association.
From the analysis of drought tolerance in paddy rice, the drought tolerance of the first paddy rice was highest during the panicle differentiation stage and was lowest during the tillering stage. The drought tolerance of the second paddy rice was highest during the mellow stage and was lowest during the panicle differentiation stage.
For the analysis of water distribution and management, The result shows that the water distribution model, as proposed in this study, is capable of calculating the field irrigation water requirements for the irrigation on mixed-cultivation tertiary blocks in considerable scale, and by introducing the Modified K-factor as an index, appropriate amount of irrigation water could be conveyed to specific field block at the right time, fairly and rationally. In addition, the acquirement of sufficient irrigation water for the crops in planting groups among rotation groups is assured, such that water resources during drought periods could be effectively used, and the water distribution at variant flow situation is resolved.
Subjects
混植
田間灌溉需水量
配水
Field Irrigation Requirement
Water Distribution
Type
thesis