Shannon's diversity index H' = pi log 2 pi was calculated for 16 fish species. The index was resolved into its components, species richness and relative abundance, to determine which components played a larger role in the determination of diversity pattern. Changes in diversity were correlated with species richness (r), habitat heterogeneity, and hydrological regimes in a longitudinal stretch of 35 km along the river Giri, a major tributary of the Yamuna River system, in Western Himalayas. Abundance differs with change in habitat structures, habitat preference of fish species and water regimes. The decrease in diversity in the lower stretch of about 3-4 km upstream of the barrage was found to be associated with habitat fragmentation and as well as d/s with loss of biotic integrity of aquatic ecosystem due to water scarcity. Species richness was found to be maximum at upper and middle reaches (elevation 650-800 m, msl) of the river, whereas it was low in lower reaches. Change in water chemistry was also noticed at Jatan barrage-low head dam due to impoundment of river water. It is inferred that the regulation of water has an impact on species richness and relative abundance, and on habitat heterogeneity which has decreased due to the change in environmental condition.RÉSUMÉ: Impact des barrages de seuil sur les pêcheries -Etude de cas sur la rivière Giri du bassin de Yamuna, en Inde. L'indice de diversité de Shannon H' = pi log 2 pi a été calculé pour 16 espèces de poissons. L'indice a été résolu dans ses composantes, la richesse spécifique et l'abondance relative, afin de déterminer quelles composantes ont joué un rôle plus important dans la détermination du modèle de diversité. Les changements dans la diversité ont été corrélés avec la richesse spécifique(r), l'hétérogénéité de l'habitat et les régimes hydrologiques sur un secteur longitudinal de 35 km sur la rivière de Giri, un des tributaires majeurs du bassin hydrologique de Yamuna, dans le Ouest des Himalaya. L'abondance diffère selon les changements dans les structures des habitats, les préférences d'habitat des poissons et les régimes hydrologiques. La baisse en diversité dans le secteur inférieur à 3-4 km en amont du barrage a été associée avec la fragmentation de l'habitat et le rapport d/s a été associé avec la perte d'intégrité biotique de l'écosystème aquatique à cause du manque d'eau. La richesse spécifique a atteint la valeur maximale dans les secteurs supérieur et moyen de la rivière (altitude 650-800 m au-dessus du niveau de la mer) et elle est basse dans le secteur inférieur. De même un changement dans la chimie de l'eau a été détecté au barrage de seuil de Jatan, dû à la retenue d'eau de la rivière. On considère que la régularisation de la rivière porte atteinte à la richesse spécifique et à l'abondance relative ainsi qu'à la hétérogénéité de l'habitat, qui a baissé à cause des changements des conditions environnementales.Brought to you by | MIT Libraries Authenticated Download Date | 5/13/18 12:09 AM H. S. Rumana et al. -Dam impact on ...

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Asan wetland is one of the biodiversity hotspot and ecologically sensitive habitat in Doon valley and this important Bird Area has been notified as an 'Asan Conservation Reserve' in Uttarakhand, India. Its water is used for drinking, irrigation, boating and recreation. In view of the above, an attempt was made to study certain limnological parameters to assess the nutrient status for its suitability from ecological point of view, drinking and irrigation purpose. The limnological parameters were seasonally examined following standard methods. Total 72 water samples were collected from eight sampling stations. Study revealed that most of the parameters were in the limit of standard except some parameters like BOD and COD (higher in monsoon season). NO 3 and PO 4 3were found higher which can cause eutrophication in the water body. The wetland water was found to be slightly alkaline (pH 7.6) except in monsoon season and moderately hard (122.4 mg/l). Physico-chemical parameters indicate prevalence of good quality of water except in monsoon season in Asan wetland.

Asan wetland is a man-made wetland located in Uttarakhand state. In the given study, efforts have been made to study the floristic diversity and species composition of the aquatic macrophyte in Asan wetland and provide a check list. Sixty seven species were recorded under 32 families being maximum in Cyperaceae followed by Poaceae and Asteraceae. Remaining families comprised either one or two species each. Among all the recorded species, monocots (54%) were dominated over dicots (42%) and remaining 4% comprised ferns. Herbaceous macrophytes were found growing abundantly (54%) which are followed in degree of prevalence by the grasses (21%), sedges (18%), shrubs (4%) and climbers (3%). In addition, this study also revealed that pollution resistant species like Bacopa monnieri, Hydrilla verticillata, Vallisneria spiralis and Eichhornia crassipes along with tall grass species which grow in shallow water are spreading considerably that indicates an increasing pollution in the wetland. The present study will provide an important set of informations to support research work like limnological studies, productivity, conservation and management programs of this wetland.