In-situ capturing of rains is no doubt considered most advantageous technological option from soil and water conservation point of view, and also vital principle of watershed management. It requires small small water harvesting structures and dams, where we often take a bit liberty to design them for a low recurrance intervals and other factors , giving a balance in 'risk of failure' as well as 'estimated cost'. The real beauty of ' Small Dams'
things are entirely different in case of 'Big dams'. But they too are extremly important to generate reservoir storage and feed canal irrigation and hydropower. They have their pros and cons in terms of cost and environment concerns.
A big argument ...weather 'small dams' are more desired or ' big dams' if both what shall be the logical rationing....considering dry and non dry regions...
You are raising an important related to dams - scale. Dams have so many benefits and costs that scale plays a major role. Small dams have many benefits at a local scale and often recommended for landscapes with deficit water supplies. Large dams have multiple benefits but more recently are a focus of debate. A major issue is disruption of the river ecology and retention of sediment that otherwise reaches the coast. While big dams can have substantial economic and hydrologic gains to a developing region, there is varied in response by countries. Most developed economies have stopped building big dams while many large dams are being constructed or being planned in future. Reasons of developmental and water supply gain is an argument to boost a region. The long--term cost on ecosystems, cumulative costs, and other impacts are often ignored in countries needing changes in water supplies and development needs. Small-scale dams could be used strategically to achieve many benefits that dams could provide but could be designed to minimize ecosystem impacts.
Thank you for question,What do you mean by big and small Dams (volume of reservoir).
Here it is needed to understand the different between big macro and micro dams, so macro or big dams that dams built for purposes of river regulations, flood prevention, flow regulation, power generation and so on of large-scale objectives, but this big dams have also some negative ecological consequences such as increasing water salinity, decreasing the solid runoff, salinity of soil as in the adjacent territories as in the whole basin of river especially in the deltas, desertification and so on.
But the micro or small dams or construction for rain water harvesting to improve natural plant cover and biodiversity, groundwater storage capacity..... so it is totally different concept and in my opinion there is no contradiction between them.
Thank you Randhir..I totally agree by saying a simple but effective proverb..
"Small is always beautiful" but "bigger is not always beautiful"
catching a drop at a point where it falls and at a time when it falls from sky is the best strategy. if we can do that I do not think that we need to go for high costs big dams..see not only cost they have infinite number of issues.....one example I am giving..is the dislocation of lakhs of people and their houses which comes under submergence at up stream locations , when ever one plan a big dam on ariver in first stage. and then consistently increasing the dam height years to years. What I guess from my seen and realized views , that even a single centimeter increase in big dam height may give enormous hikes in submergence area and many cost ingredients , which not always matches with claimed benefits like increased storage or increased command. area
Ahmad thanks for a different comment. you are correct in one way. but in some of the situation there exists a vast and most sensitive contradiction because not only science but the society and politics too make entry in that domain. example i have given say increased height dams affects area under submergance shifting of many people and land use conversions to a great extent..this whole creates a big contradiction bewteen small and big dams ...more true for tropical water deficit populated nations like india.
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