Most part of the world regularly experience droughts or floods or both and suffer due to "too less or too high water syndrome" and groundwater management issues in recent years, which warrant prudent implementation of soil and water conservation measures. Water Harvesting (WH) has increasingly become a means to tackle the problems of drought, water scarcity and sometimes to mitigate floods in most parts of the world. The WH is known to provide many direct and indirect benefits to farmers, ecosystems and the general public. Many Asian and African countries including India have rich tradition of WH and recycling to improve crop production and livestock raising. About 20% of rain water is observed to be harvested annually and roughly about 1 ha-m water can be harvested from every 10 ha watershed area in Doon valley, foothill Himalayas. Fish farming in Water Harvesting Structures (WHSs) using appropriate technologies would enhance benefits of WH and provide food and economic returns to the farmers and farming communities. The refined package of practices for carp culture in farm ponds and WHSs yielded 3.5-4.5.0 t fish ha-1 year-1 with a net annual profit of about Rs. 90,000-1,00,000 ha-1 and BC ratio, 1.9:1 in Doon valley.
A survey of 20 water conservationists, 18 WHSs and 12 published reports on Integrated Watershed Management (IWM) analysis indicated varying preferences or justifications and prevailing interfaces on design or construction criteria of WHSs or farm ponds between conservationists and aquaculturists with reference to various spheres of water conservation vis-à-vis fish farming, especially in north-western Himalayas, India. The pooled score of conservationists, published literature and existing WHSs for the preferences on different design features of WHSs, viz., water allocation, direction or orientation, size, shape, depth width, area versus volume, type of pond bottom etc. to benefit construction or water conservation efforts ranged 15-80%. No specification for direction, preference for more depth and small size outlet disproportionate to size of ponds had higher score over 80%. Comparing the needs of WHSs for water conservation and fish farming identified the critical need for specific assumptions and compromises on engineering design and management of WHSs between the two avenues to maximize benefits.
Principles of WH and design features of WHSs will be presented drawing a comparison of WH and WHSs for water conservation and accommodative aquaculture, especially under watershed management programs in developing countries and water scarce regions of the world. Engineering perspectives of WHSs or farm ponds to accommodate aquaculture besides types, benefits, and impacts of WH and WHSs are discussed in light of available literature or expert judgment favorable for both aquaculture and watershed engineering principles.