Rivers

The study deals with the development of an operation policy for the Tawa dam. It adopts rule-curve based policy for conservation regulation of the dam developed for three levels viz. upper rule level, middle rule level (critical for irrigation) and lower rule level (critical for water supply and upstream use). The generated simulation model developed by the Water Resources System Group at the National Institute of Hydrology is used to simulate the system operation and to refine the rule curves.

The study deals with flood plain mapping in a part of Yamuna basin between Gangoh and New Delhi. A flood is a markedly high stage of flow in a river and may inundate adjoining lands, which is called the floodplain of a river. So, floodplain is land inundated by a flood of given frequency. Alternately it is also defined as flat land between valley walls.

In this study, HEC 2 programme has been implemented on river Digaru to compute flow regime or the water surface profile for various discharge conditions. In this reach, two bridges have been considered to compute water surface elevations, critical water surface elevations, energy grade elevations & slope, velocity in the channel, flow area, top width and Froude Number.

This is the first in a new series of articles that IWP will host on various aspects of Environmental Flows. We welcome your comments and original articles for this series, please mail us at portal@arghyam.org

The other side of the story: Free-flowing rivers around the world

With around 5100 large dams, India ranks third in the world with regards to the number of large dams. The ongoing debate over the economic, social and environmental costs of large dams has indicated many times that these costs are not commensurate with their benefits. Although we have dammed all our major rivers, (except Brahmaputra and plans to dam its major tributaries are on way, some like Ranganadi have already been dammed), profoundly changing their hydrological, ecological, social and cultural systems, we are yet to form a policy which states that environmental flows in rivers are a necessity. It is more than clear now that environmental flows relate to well being of not only ‘birds and fishes’, but also of the entire human society . Take an example of fisheries, lack of flows in rivers and contractor-owned reservoir fishing has affected the livelihood of hundreds of thousands of small fishermen . Environmental flows also dilute pollution load, so let us not hide behind the fact that pollution is wiping out our riverine fish, not the absence of flows. It is also clear that environmental flows do NOT mean a decommissioning of all the present dams, nor do they mean any random figure like 60% or 10% of MAR . Eflows require reaching a wise compromise through science and local negotiations, for each river.

While many countries have put in place policies and laws for maintaining environmental flows in their rivers, there is also a rarer category: Rivers which have not been dammed yet, rivers which retain their connection from the source to the sea, nurturing myriad ecosystems and communities in their wake! These are known by many names like Free flowing rivers, Wild Rivers, Pristine/ Virgin rivers, Heritage Rivers, etc., each indicating their rare character and value. In ecological and cultural terms, the value of these rivers is immense and as more and more rivers are being dammed the world over, this value is increasing steeply. Unfortunately, in today’s economic terms, these rivers are still waiting to get their due recognition, but as human systems evolve, they will surely be seen as ‘invaluable’ service providers with phenomenal use and non use values.

Organizer: Wageningen UR Centre for Development Innovation

Topics:

• Concepts in wetland and river basin management
• Facilitation of multi-stakeholder processes
• Fieldwork wetland management
• Adult education and social learning
• Curriculum development

The study deals with dam break analysis of Barna dam located in the state of Madhya Pradesh carried out using the popular National Weather Service Dam Break Flood Forecasting (NWS DAMBRK) model to assess the likely maximum flood discharge and elevation to be attained in Bareli township, 22 km downstream of the dam.

The study deals with flow computation in Saptamukhi river estuary in Sunderbans delta of West Bengal using finite element method. Complex interactions between physical, chemical and biological processes are present in coastal areas. Water circulation is one of the most important factors controlling these processes. The study of the real hydrodynamic regime and proper management of estuaries, lagoons and coastal regions due to high tides, peak flows erosion, sedimentation and pollutant load discharges is vital.

The report presents flood plain mapping of Phulbari area within the flood plains of Brahmaputra basin in the States of Assam and Meghalaya using satellite data. Flood is a natural calamity in which most parts of the north-eastern region are ravaged. Management of the problem in these disastrous flood affected areas often requires flood plain mapping for protection and resource development. This has mostly being done in real time on the basis of time consuming and often hazardous ground based surveys.

The report deals with estimation of evaporation losses from water surface in Tawa reservoir in Hoshangabad district of Madhya Pradesh. The study is third in the series of evaporation studies to assess the adaptability of different methods for estimation of evaporation from free water surfaces in semi-arid areas. The estimates of evaporation from free water surface obtained by four methods namely Penman, Kohler, Van Bavel and Morton are compared with observed pan values on monthly, seasonal and annual basis.

The report deals with Geographical Information Systems (GIS) based rainfall-runoff modeling using Topography Model (TOPMODEL) for the Hemavathy catchment of Cauvery basin in Western Ghats of Karnataka. The TOPMODEL is a variable contribution area model in which the predominant factors determining the formation of runoff are represented by the topography of the basin and a negative exponential law linking the transmissivity of the soil with the vertical distance from the ground level.