缺水期之灌溉用水有效調配模式

An Efficient Irrigation Water Distribution Model in Water Short Environment

陳清田(Ching-Tien Chen)

指導教授 ： 甘俊二

國立臺灣大學/生物資源暨農學院/生物環境系統工程學研究所/博士(2004年)

https://doi.org/10.6342/NTU.2004.02384

摘要

灌溉之主要目的乃在提供足夠之水分，以維作物正常之生長，進而確保其產量，然台灣地區由於受到地形、地勢與降雨時空分布不均等因素之影響，可資利用之水資源常處捉襟見肘。因此，台灣各農田水利會於執行灌溉計畫時，大都以水源供給面為基礎之灌溉率，作為該區執行灌溉管理之依據，此方式雖具有操作之方便性，然因受於水源水量之限制，故尚未能完全滿足作物生長之用水需求，就長時間而言，對水土資源之永續利用將有一定程度之影響。環顧現今世界灌溉之大環境潮流，灌溉用水之考量，皆以田間作物用水需求為基礎，配合水利會現有之灌溉系統，建立一套以需求為導向之田間灌溉需水量推估模式與滿足田間供需平衡之灌溉用水調配模式，此乃從事農業水資源規劃研究者刻不容緩之要務。
近年來，台灣地區由於受到世界貿易組織(WTO)衝擊與溫室效應之雙重影響，未來之農業生產結構與水資源量之分佈，勢必有所改變，故如何藉由灌溉用水有效調配管理，以確保作物於任一生長階段之用水需求，進而提昇農業產值及維持農田之永續經營，是急需且必要之研究方向。今為提昇農業產值之競爭能力，作物多樣化已是必然之趨勢，惟此將使灌區混植情形日趨嚴重，致灌溉配水作業更形不易，故如何建立一符合混作灌區多樣化作物用水需求之灌溉用水調配模式，實為現階段一重要課題。
因此，本研究之目的，首先蒐集研究區內之氣象記錄、土壤質地、有效雨量、灌溉面積、作物類別等資料，建立一滿足多樣化作物生長需求之混植灌區灌溉需水量推估模式，冀以快速、準確推估水、旱混植灌區之灌溉需水量，進而解析台灣地區各農田水利會合理之灌溉需水量，俾為溉配水計畫之應用；其次以盆栽試驗，解析在不影響其農業生產條件下，水稻於成活期、分蘗期、幼穗形成期、抽穗期及乳熟期等重要生育階段之最大輪灌期距，俾供灌溉配水模式之應用；最後，探討在田間用水供需平衡之條件下，考量灌區面積大小、水路長度、作物類別、耐旱容陷褻Z及系統別，比較分析修正k係數法與k係數法於幹、支線系統配水之效率，並佐以實地調查之資料，進行模式引證工作，期能建立一確保多樣化作物用水需求且符合變動水源水量之機動性灌溉配水模式，解決水稻旱作混作灌區之灌溉配水問題。
研究結果顯示，由台灣各農田水利會灌溉用水現況分析得知，於相同之計畫灌溉面積下，以確保作物正常生長為基礎所推得之理論計畫灌溉用水量，皆較計畫灌溉用水量與實際取水量高出甚多，尤以灌溉面積較大之嘉南、雲林及彰化農田水利會更甚。於水稻之耐旱分析而言，一期作水稻之耐旱性以幼穗形成期較高，而以分蘗期為最低，第二期作之耐旱性則以乳熟期為最高，而以幼穗期形成期為最低。就灌溉用水有效調配分析，無論是支線配水或幹線配水，以修正K 係數法所得之配水效率皆較傳統之K 係數法為高，故以修正K 係數做為配水之指標，除可將水公平、合理、適時、適量且更有效率地分配至各混植田區，並可確保在分組輪灌時，當值組之田間作物在灌溉期間能獲得充分之灌溉水量，讓水資源在缺水期間得以充分有效之利用，達到配水之目的，解決不定流量合理配水之問題，尤其當嚴重缺水時，則幹線配水之效率遠較支線配水為佳。

關鍵字

混植 ； 田間灌溉需水量 ； 配水

並列摘要

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.

並列關鍵字

Field Irrigation Requirement ； Water Distribution

參考文獻

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