ModelsThe Beaverkill Watershed in the Catskill Mountains of New York, U.S.A., showed evidence of high summer stream temperatures throughout critical trout habitat (Gardner, Sullivan and Lembo, 2003). Because habitat quality dramatically influences trout communities, it is important for biologists to identify and map these characteristics and to monitor how they change over time.Seventy-two temperature loggers were placed throughout the watershed during the summer of 2000. Three geostatistical metrics for predicting temperature across the watershed were constructed and evaluated. The first metric utilized the shortest path between temperature loggers without using stream network information. A second metric used distance calculated along the stream network in both upstream and down stream directions. The final metric was a modified network system in which the distances were weighted by stream order. The authors found that each metric provided a predictive capability, with added complexity improving the accuracy of represented stream temperatures. 2492Tamil Nadu Electricity board (TNEB) has two power stations located at Ennore, about 15 km North of Chennai (Ghosh et. al., 2003). Both the power stations are operating on once through cooling water systems and are drawing required cooling water from Ennore creek. However, due to frequent choking of creek mouth, both power stations are experiencing acute shortage of the requisite coolant water. Physical Thermal Model studies were carried out for five different alternative locations of intake and outfall, constructed to the scales 1:360 (Horizontal) and 1:80 (Vertical). The model results revealed that surface heal loss played a dominant role in the reduction of temperature. The optimum area of Ennore creek mouth to be maintained is 50 sq. m for effective utilization of tidal water and it was found that the withdrawal of cooling water from the port basin and discharge of warm water at Ennore creek near the mouth is the most suitable solution for supplying cooling water for both the power plants.Mathematical functions developed in long-term laboratory experiments at different constant temperatures were combined with daily water temperatures for 1991-93 in eight Austrian streams and rivers to simulate the complex life histories and reproductive capacities of two freshwater amphipods: Gammarus fossarum and G. roeseli (Pockl, Webb and Sutcliffe, 2003). The functions describe brood development times, hatching success, times taken to reach sexual maturity, growth, and fecundity. Simulations included summer-cold mountain streams, summer-warm lowland rivers, and water courses fed by groundwater or

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