Guidelines for drinking and irrigation water projects
The general guidelines for water usage in different sectors are given
Adequate safe drinking water facilities should be provided to the entire population both in urban and rural areas. Irrigation and multi -purpose projects should invariably include a drinking water component wherever there is no alternative source of drinking water. Primarily, the water stored in a reservoir has to be extracted using a suitable pumping unit and then conveyed to a water treatment plant where the physical and chemical impurities are removed to the extent of human tolerance. The purified water is then pumped again to the demand area, that is, the urban or rural habitation clusters. The source of water, however, could as well be from ground water or directly from the river. The aspect of water withdrawal for drinking and its subsequent purification and distribution to households is dealt with under the course Water and Waste Water Engineering. The following books may be useful to consult.
Irrigation planning either in an individual project or in a basin as whole should take into account the irrigability of land, cost of effective irrigation options possible from all available sources of water and appropriate irrigation techniques for optimizing water use efficiency. Irrigation intensity should be such as to extend the benefits of irrigation to as large as number of farm families as possible, keeping in view the need to maximize production.
Water allocation in an irrigation system should be done with due regard to equity and social justice. Disparities in the availability of water between head-reach and tail-end farms and (in respect of canal irrigation) between large and small farms should be obviated by adoption of a rotational water distribution system and supply of water on a volumetric basis subject to certain ceilings and rational water pricing.
Concerned efforts should be made to ensure that the irrigation potential created is fully utilized. For this purpose, the command area development approach should be adopted in all irrigation projects.
Irrigation being the largest consumer of freshwater, the aim should be to get optimal productivity per unit of water. Scientific water management, farm practices and sprinkler and drip system of irrigation should be adopted wherever possible.
Research on institutional arrangements for water allocation covers three major types of water allocation: public allocation, user-based allocation, and market allocation. This work includes attention to water rights and to the organizations involved in water allocation and management, as well as a comparative study of the consequences of water reallocation from irrigation to other sectors. A key aspect of this research is the identification of different stakeholders' interests, and the consequences of alternative institutions for the livelihoods of the poor.
Rotational water distribution system: Water allocated to the forms one after the other in a repeated manner.
Volumetric basis: Water allocated to each farm a specified volume based on the area of the farm, type of crop etc.
Irrigation is the process by which water is diverted from a river or pumped from a well and used for the purpose of agricultural production. Areas under irrigation thus include areas equipped for full and partial control irrigation, spate irrigation areas, equipped wetland and inland valley bottoms, irrespective of their size or management type. It does not consider techniques related to on-farm water conservation like water harvesting. The area which can potentially be irrigated depends on the physical resources 'soil' and 'water', combined with the irrigation water requirements as determined by the cropping patterns and climate. However, environmental and socioeconomic constraintsalso have to be taken into consideration in order to guarantee a sustainable use of the available physical resources. This means that in most cases the possibilities for irrigation development would be less than the physical irrigation potential.
Command area development:
The command area development programme aims mainly at reducing the gap between the potential created for irrigation to achieve higher agriculture production thereof. This is to be achieved through the integrated development of irrigated tracks to ensure efficient soil land use and water management for ensuring planned increased productivity.
Sprinkler irrigation offers a means of irrigating areas which are so irregular that they prevent use of any surface irrigation methods. By using a low supply rate, deep percolation or surface runoff and erosion can be minimized. Offsetting these advantages is the relatively high cost of the sprinkling equipment and the permanent installations necessary to supply water to the sprinkler lines. Very low delivery rates may also result in fairly high evaporation from the spray and the wetted vegetation. It is impossible to get completely uniform distribution of water around a sprinkler head and spacing of the heads must be planned to overlap spray areas so that distribution is essentially uniform.
The drip method of irrigation, also called trickle irrigation, originally developed in Israel, is becoming popular in areas having water scarcity and salt problems. The method is one of the most recent developments in irrigation. It involves slow and frequent application of water to the plant root zone and enables the application of water and fertilizer at optimum rates to the root system. It minimizes the loss of water by deep percolation below the root zone or by evaporation from the soil surface. Drip irrigation is not only economical in water use but also gives higher yields with poor quality water.
Participatory approach to water resource management
Management of water resources for diverse uses should incorporate a participatory approach; by involving not only the various government agencies but also the users and other stakeholders in various aspects of planning, design, development and management of the water resources schemes. Even private sector participation should be encouraged, wherever feasible.
In fact, private participation has grown rapidly in many sectors in the recent years due to government encouragem-Own-
Transfer (BOT)” has been popularized and sho concept may be actively propagated in water resources sector too. For example,
in water scarce regions, recycling of waste water or desalinization of brackish water, which aremore capital intensive (due to costly technological input), may be handed over to private entrepreneurs on BOT basis.