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In the arid and semi-arid tropics, low annual rainfall together with high intensity rains has resulted in excess runoV, soil erosion and low moisture intake leading to poor crop yields. Therefore, adoption of soil and water conservation measures is necessary for the optimal utilization of natural resources and to increase the productivity of land on a sustainable basis. Remote sensing and G IS techniques can be used for generating development plans for the watershed area in consonance with the production potential and limitation of terrain resources, and can also be used for assessing the impact of these measures before actual implementation in the eld. This paper describes a case study for the Jasdan taluka (district ) of Rajkot in G ujarat, India. The aims are to prioritize watersheds on the basis of runoV generated, expressed as yield, due to existing land use conditions; to suggest soil and water conservation measures; and to evaluate the hydrologic response of these measures on runoV. The Soil Conservation Service Curve N umber (CN ) method was used for computing the runoV; subsequently runoV yield in percentage was calculated for prioritizing the watersheds. Satellite and other collateral data were used to identify the problems and potential in the watersheds and recommend measures for soil and water conservation. The impact of these measures was assessed by computing runoV under alternative land use and management practices. It was found that the runoV yield decreased by 42.88% of the pre-conservation value for the watershed.*Currently on leave from ISRO . P resent address: D epartment of G eography, 217-1984, West M all,

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A methodology was developed for large area yield forecast using a crop simulation model and a discrete technology trend, and was applied to the coherent wheat yield variability zones of Eastern Uttar Pradesh, India. The approach consisted of three major steps: (a) prediction of technology trend yield using historical yield series of the region; (b) prediction of weather-induced deviation in wheat yield using CERES-Wheat simulation model and relating weather-induced deviation in simulated yield to deviation in observed yield deviations from technology trend; and (c) final yield forecast by incorporating predicted yield deviation in trend predicted yield. The regression coefficients for step (b) were generated using 10 years' data (1984/85–1994/95) and the reliability of the approach was tested on a data set of 5 years' independent data (1995/96–1999/2000). The results showed that this approach could capture year-to-year variability in large area wheat yield with reasonable accuracy. The Root Mean Square Error (RMSE) between observed and predicted yield was reported as 0·098 t/ha for the mean yield of 2·072 t/ha (4·72%). However, the RMSE was slightly higher in the forecasting period in comparison to the calibration period. The use of this methodology for issuing the pre-harvest forecast and the effect of upgrading the technology trend were also studied. The pre-harvest forecasts were made using in-season weather data up to the end of February and climatic-normal for the rest of the wheat-growing season, which showed good agreement with observed wheat yields. The forecasts of wheat yield for the season 1999/2000 were made using the technology trend up to 1994/95 and the updated technology trend up to 1998/99, which showed that the RMSE fell in the latter case, from 4·10 to 2·50%.

Wood density measurements on green and ovendry volume bases were made and their variations were statistically analyzed for six major tree species of the Northwest Territories. These values, based on samples from 336 trees, showed that the species had highly significant (P < 0.01) differences in wood densities when compared at each of the 10 sampled relative height positions along the tree stem. For tree bole locations near the bottom, there were highly significant (P < 0.01) differences among various diameter size classes, but these differences decreased in significance toward the top. A predictor model was derived for estimating volume-weighted average basic wood density of a tree from its basic wood density at breast height. The lowest wood density in the majority of the species was in a band of varying length including or approaching the midpoint of the tree bole. Such information on density gradients is useful in allocating parts of a tree for optimum use.