A study of Reservoir's Life and Possible Measures to Decline Sedimentary Rate of Small Reservoirs in the East   Rungkarn Krishnamra, Ratana Jindapol, Piboon Sriskul and Uthai Somsopon   ABSTRACT         In the study of sedimentary rate of three small reservoirs (Type III- Hill) in agricultural watersheds in the East. Under the criteria of       1) Annual rainfall average of 1,141.3 to 1,276.4 millimeter,       2) Soil series in the upper watershed area as Mab Bon, Sattahip, Satuk, Hupkrapong and Slope complex,       3) Watershed size of 0.20 to 5.86 Square-Kilometer and       4) Landuse system of field crops and orchards.       The effective life of these reservoirs are ranged from 16 to 73 years. The appropriate soil and water conservation measures applied to maintain fertility of every soil type in the watershed area such as crop rotation, contour strip cropping and terracing are the important issues. They can decrease soil erosion rate at the surface and prolong the period of effective life of reservoirs in the watershed area.         Keywords: Reservoir's life, Small reservoir