ทรัพยากรน้ำและการใช้ประโยชน์ที่ดินในลุ่มน้ำแม่พร้าวบ้านงิ้วเฒ่า ตำบลแม่สาบ อำเภอสะเมิง จังหวัดเชียงใหม่

Abstract

The objectives of the study on water resource and land use of Mae Phrao watershed at Ngiew Thao village, Mae Saab subdistrict, Samoeng district, Chiang Mai province were to quantify watershed forest ecology, which was the Hill evergreen forest, in relation to water quality, water quantity and agricultural land use. The methodology included 1) preliminary surveys for collecting data of the village and watershed, 2) land use inventory by ground survey and semi-structured interview, then watershed land use mapping by satellite imageries using ArcMap 10.3.1 program, 3) assessment of watershed forest ecology by Participatory Ecological Investigation Methodology (PEIM) with key informants using stratified random sampling and simple random samlping to set up 2 sample plots (quadrat format) which were selected according to the watershed forest size of 2.3287 km2. Each quadrat was 40 ×40 m2 for collecting ecological variables and analyzing forest abundance by applying formulae of Importance Value Index (IVI) and Species diversity index, with particular to Shannon-Wiener Index (SWI), 4) assessment of physical and biological water qualities by aquatic microinvertebrate surveys, and 5) water quantity assessment by area – velocity method. The results showed that Mae Phrao watershed area was 5,014.50 rai or 8.0232 km2, including the forest land of 4,455.56 rai accounting for 88.85% of the total land, paddy areas of 227.33 rai, crop and orchard areas of 137.62 rai as 4.53% and 2.75% of the total land respectively, and community ซ and homestead areas of 193.99 rai as 3.87% of total land. Mae Phrao watershed forest was 1,455.44 rai accounting for 29.02% of the total land. The SWI was 5.18 considering as relatively high, based on the standard values of 1-7. There were 376 trees of 67 species in 36 families. The species with the highest relative Important Value Index (relative IVI) was Schleichera oleosa (5.53%) followed by Shorea siamensis, Colona flagocarpa, Castanopsis acuminatissima, Lithocarpus truncatus and Aporosa villosa accounting for 5.15%, 4.98%, 4.96%, 4.82% and 3.74% respectively. In agricultural land use, the important crops were paddy rice, garlic, vegetable soybean and peanut. The villagers divided their paddy areas into 22 fields using local names, which had intensive farming along the stream banks. The water quality of Mae Phrao stream was good, which average biological index was 5.99, while the watershed forest had the best water quality (biological index: 7.40). The total streamflow quantity of Mae Phrao watershed was 2,634,369.30 m3/year. The farmers of Mae Phrao watershed utilized water for agriculture by direct pumping and “Muang – Fai system”, plus additional water transporting pipeline from Mae Khae reservoir. The farmers managed their water resource by participatory approach. The estimation of water requirement for agriculture showed that water usage was 571,052.96 m3/yr. The watershed forest produced abundant water, which was more than the farming needs and then fed into Mae Khae stream flowing down to Mae Khan stream prior to the Ping river. In conclusion, Mae Phrao watershed forest was abundant and capable to produce good water qualities, both physical and biological characteristics. Water supply was available all-year-round, yielding the perennial stream type. The villagers were aware of the importance of forest resource conservation, particularly the watershed forest. They also understood the benefits of water quality and streamflow which related to the good-condition watershed forest. The entire community thus participated in water resource management efficiently, by integrating updated irrigation technology with their local knowledge, regarding the Muang – Fai system. The farmers planned their cropping system calendar and selected crop species with consideration of water discharge. Natural resource management by the villagers of Mae Phrao watershed initiated the balance between land use and natural resource conservation, enabling abundant watershed and sustainable livelihoods of the villagers in the future.