Agricultural Water Resource Risks from Rainfall Variability in the Upper Mae Pae Watershed, Chom Thong District, Chiang Mai

Abstract

The purpose of this research was to study the risks of rainfall variability on the availability of agricultural water resources that could identify indicators leading to a sustainable water management plan for the upper Mae Pae Watershed. The research process focused on learning from and analyzing problems with stakeholders through academic sources and empirical data to analyze changes in rainfall behavior from climate variability data from 70 years, including an analysis of watershed hydrological characteristics and water balance in the agricultural sector.

 The study's results revealed several risks to water resources in the agricultural sector of the upper Mae Pae Watershed as follows: 1) The average rainfall trend in the last 15 years (from 2007–2022) decreased to only 862.43 mm/y. This amount of rainfall was below the criteria for drought (less than 900 mm/y). The decline in rainfall was influenced by 16 El Niño events, each leading to prolonged droughts lasting for more than 20 weeks; 2) The period of runoff was uneven throughout the year, with runoff occurring predominantly during the rainy season, leading to an an annual water deficit of 0.84 million cubic meters from November to April. Farmers in the area required 1.21 million cubic meters of water during this period for crop cultivation, while only 0.37 million cubic meters were available; 3) Khun Pae Reservoir and Ton Phueng Reservoir were too small to distribute water during the dry season. Additionally, the pool system faced problems in terms of both the number and location of water distribution points, resulting in an uneven and insufficient water allocation and        4) Farmers in the upstream area pumped water from Khun Pae Creek for crop cultivation during the dry season. This practice led to misunderstandings and conflicts among farmers in the upstream and downstream regions, exacerbating water resource challenges. The aforementioned water resource problems were the key factors leading to the development of the agricultural water management plan to ensure the sustainability of water resources in the upper Mae Pae Watershed.