Some results and calibration equations based on the data of pretreatment period (1979-1985) are summarized. The project \vas designed and executed in order to study the effects of forestry operations on streamflow and water quality. Coefficients of correiation and regression were highly significant. Coefficients of monthly variation of nutrient flux and sediment yield were extremeiy high. The highest mean discharges of ions in kg/ha/month vvere H C 03 (11.5) and C1 (8.6) in both VV-I and W-IV. Few data are currently avaiiabie about the hydrologic characteristics, nutrient Chemical discharges, suspended sediment and water yields as influenced by forest types, forestry operations and species conversions on small watersheds under indigenous forest ecosystems in Turkey. Balcı and Özyuvacı (1976) have first documented the nutrient flux and suspended sediment discharge from the Arnavutköy municipal vvatershed dominated by deciduous coppice near İstanbul. The other noticible data and some initiai results were published by Balcı, Özyuvacı and Ozhan (1986) based on a comprehensive experimental watershed study initiated in the Belgrad Experimental Forest near İstanbul. The quality \vater supply in ever expending greater İstanbul has ahvays become a vital problem. Since late 1960's extensive degraded deciduous forest areas in the municipal ıvatersheds have been converted to the fast-growing conifers by using the mechanized plantation techniques. Besides such drastic changes in the forest cover, other disastrous activities like unhealthy urbanization and some land use practices have been exerting great impact upon ıvater resources.
A long-term experimental watershed research project therefore was initiatcd in 1979. Five small adjoining cafchments tributary to Ortadere creek ranging from 17.50 to 77.50 hectares in area were selected within the Belgrad Experimental Forest in order to study the effects of forestry operations and the conversion of natural hardwoods to fast growing conifers upon streaınflow, \vater and water yield. This paper presents some of the results obtained during the calibration period between 1979-1985, mainly on calibration equations, streamflovv, suspended sediment and nutrient discharges from only two experimental vvatersheds W-I and W-IV.