Watershed management research on mountainous land

1) Pore-Size Distribution of Natural Hill-Evergreen Forest and Shifting Cultivation Soils at Doi Pui, Chiangmai : Total porosity of hill-evergreen forest soil (A, B1, B2 and B3 profiles) decreased from 0.64, 0.59, 0.54 and 0.49 % to 0.57, 0.54, 0.49, 0.44 % respectively after the utilization of land had been changed to shifting cultivation area. Quick drainage pores (30 mum) decreased abruptly in A and B1 horizons from 18 and 10 % to 9 and 6 % respectively. Slow drainage pores in A horizon, on the other hand, increased 2 % from 14 %. Pore-size distribution index in A and B1 horizons changed from 0.7 and 0.84 to 1.21 and 0.86, but B2 and B3 horizons didn't change by these impacts. The interpretation of these numbers designated that well-developed structure of hill-evergreen forest soil became poor structure and this affected the permeability of water in soil. 2) Impact study of various land use patterns on physical properties of water was conducted at Doi Pui Chiengmai : in the watershed areas of hill-evergreen forest,wild peach orchard, and Mao hill-tribe village. Physical properties of water were separately analyzed by color, turbidity, pH, temperature hardness, and electrical conductivity. Water color was quantified the highest value at Mao hill-tribe village 99.83 units and varied evidently with monthly rainfall, wild peach orchard 57.08 units and hill-evergreen forest 22.67 units the least. Turbidity also found the same trend of water of water color, Mao hill-tribe village had the highest value (13.2 JTU), and hill-evergreen forest (1.3 JTU) the least. Less plant cover and organic matter as well as more human activities in the Mao hill-tribe village than the other types of land use would cause higher values of color and turbidity in the streamwater. Physical properties of water in terms of turbidity, color, pH, temperature, hardness, and electrical conductivity in the hill-evergreen forest would be on standard. But streamwater in the wild peach orchard was of slightly lower standard, deposition of suspended sediment is recommended before using the water. Unfortunately, steamwater of Mao hill-tribe village was of lower standard and not suitable to use. However, streamwater of all land use types could be used for raising the animals and irrigation for cultivating crops.