台灣是世界排名第十八位的缺水國家（地區）。在一般人的印象裡，台灣地區平均每年有二千多毫米的雨量，是水資源不虞匱乏的國家。但是因為台灣地區地狹人稠、山坡陡峭、雨勢集中，再加上河川短促，大部分的雨水都迅速地流入海洋，只要久沒下雨便容易形成乾旱。因為乾旱而無法灌溉，會使得農業經濟上影響甚大，因此水資源管理是非常重要的。一般的自動灌溉系統，通常都是使用固定時間灑水，這個機制通常會因為天氣變化浪費水資源，而且也會浪費人力在注意水分灌溉跟土壤濕度上。自動偵測濕度灌溉系統雖然可以解決這個問題，但感測器(Sensor)在一段時間會固定啟動偵測濕度，而浪費很多電力。本論文提出兩種方法，第一是使得感測網路(Senor Network)裡面的感測器(Sensor)不用在固定時間量測濕度，只需要在必要偵測濕度時候喚醒起來量土壤濕度，第二是提出灑水點選擇演算法，而選擇性灑水演算法則是以(Node)節點時間的累計所計算出灑水效益值，也可以依照作物對濕度的需求做濕度門檻值之調整，並且達到減少灌溉次數並且維持土壤濕度，減少電力的消耗，並且也減少水分的浪費。

Taiwan is ranked in no. eighteen among water-scarce countries all over the world. In most people's impression, there are over two thousand millimeters of rainfall in average per year in Taiwan, and there is no shortage of water in this country. However, due to the densely population, steeped mountains, concentrated rain, and the short of rivers,most of the rainwater would rapidly flow into the ocean. In February 2015, since there was lack of rain, water was limited to different operations in Taiwan. It caused impacts on agriculture like unable to irrigate drought. It did cause a great loss on the agricultural economy. Therefore, the water resources management is very important. Generally, automatic irrigation systems are fixed time in watering. However, this mechanism usually wastes water because the weather changes sometimes and there would be actually not a need to allow fee watering. Additionally, there would be a waste of human resources to check the soil moisture with irrigation water manually. As a result, we may need an irrigation system with the function of automatically detective of humidity. However, an automatically detect humidity irrigation system needs the sensor starts in a fixed time. During the period of starting the detection, the Sensor Network would cause a lot of wasted electricity for waking up at a fixed time to detect humidity to determine whether a watering is needed. Although this approach could save water and human resources, it would increase the waste of electricity in the sensor network. Therefore, the batteries of the device needed to be changed. This paper presents a method about producing a sensor network inside the sensor at a fixed time without watering. In order to help reducing power consumption and the waste of water, the sensor would be only awaked when it is necessary needed to detect the soil moisture.
There are two methods raised in this thesis. First, the sensor can measure the moisture level without a fixed time slot in the Sensor Network. The sensor could be started working automatically when moisture level of soil has reached it's limit. Secondly, showers are worked by a formula that calculating the node of time intervals. And it would minimize the number of times and costs for showering, meanwhile keep the moisture level of soil in standard. Also, it does help saving electricity and wasting water.

參考文獻
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台灣水資源保育聯盟http://www.twwpu.org.tw/?m1=article&artid=510