Climate change has affected the temperature and rainfall characteristics worldwide. However, the changes are not equal for all regions and have localized intensity and must be quantified locally to manage the natural resources. Orissa is an eastern state in India where agricultural activities mainly depends on the rainfall and thus face problems due to changing patterns of rainfall due to changing climate. In the present study, attempts were made to study temporal variation in monthly, seasonal and annual rainfall over the state during the period from 1871 to 2006. Long term changes in rainfall characteristics were determined by both parametric and non-parametric tests. The analysis revealed a long term insignificant decline trend of annual as well as monsoon rainfall, where as increasing trend in post-monsoon season over the state of Orissa. Rainfall during winter and summer seasons showed an increasing trend. Statistically monsoon rainfall can be considered as very dependable as the coefficient of variation is 14.2%. However, there is decreasing monthly rainfall trend in June, July and September, where as increasing trend in August. This trend is more predominant in last 10 year. Based on departure from mean, rainfall analysis also showed an increased number of dry years compared to wet years after 1950. This changing rainfall trend during monsoon months is major concern for the rain-fed agriculture. More over, this will affect hydro power generation and reservoir operation in the region.

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Estimation of design flood is imperative for hydraulic designs of spillways and various other water resources development projects as well as very essential for flood risk assessment. The objective of the present study is to apply Geographical Information System (GIS) supported hydro informatics approach for estimation of design flash-flood in Bargi dam cross-section. A criterion used for estimation of design flash flood is validated by central water commission (CWC). A hydrologic modelling software (HEC-GeoHMS) is used for the delineation of basin characterises for simulation of the precipitation-runoff process of the dendritic basin system. The SUH (Synthetic Unit Hydrograph) and flood hydrographs for 25, 50 and 100 year return periods are computed along with time distribution curve which can be used to derive the time distribution co-efficient of storm rainfall in the sub-basins for the rainstorm of any duration. It is observed in this research that the peak characteristics of the design flash-flood are more perceptive to the various design storm pattern. It is demonstrated that flood hydrographs are important in flood-risk management. The results attained exhibit the capability of the flood hydrograph to describe the effects of different hydraulic systems.

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