Water Saving in Agriculture An Analytic Framework
A. D. Mohile
ANTHROPO GENIC ET Useful ET
Land Surface and Root Zone
Usable Dynamic GW
ET Without USE
SALINE GW FLOW
CAN WATER BE SAVED? •Water on earth is constant. In general, it cannot be created or destroyed. •Water in motion, through the hydrologic cycle, is more or less, constant. •But we talk about ‘creating additional resource’, destroying or wasting the resource’, etc.
•Energy cannot be created or destroyed (Newtonian physics). But, conversion of energy to unintended or non-useful form is a waste. Same analogy hold for water
Can Water be saved? (continued) • Water not used for the intended purpose is, then, a wastage, and this can be saved, to the extent possible. • This is a simplistic statement, which begs additional questions: Is there only a narrowly defined “intended purpose”? Who decides the purpose? And, what “water” are we talking about? Rain, surface or ground? “My” water or “the water”? 4
â€˘ Examples: â€˘ In a canal system, water is stolen and used for irrigating lands not in the authorised plan. For the canal manager, it is a wastage, since he did not intend this.. But, may be, for a sociologist or an agricultural economist, the intended purpose of food production and rural development is met, even though somewhat inefficiently; the water is not wasted, and the curtailment of this use is not a saving. â€˘ The wastage through leakages from surface canals, in a system, is being used for: a) Unplanned conjunctive agricultural pumping, b) Sustainance of an important wetland, or c) Industrial use. Are these wastages capable of saving?
Then What? • All viewpoints are relevant • Analyse from the point of view of each stakeholders • Carefully consider the externalities, in each frame of reference • National, multisectoral and multipurpose views are important, but these will prvail only if the decision-makers viws are not severely in conflict 6
Agricultural Water Use • Evaporation-Transpiration for meeting the physiologic processes of the desired plant species is the desired intended useof the water. • Water which does not meet this may be • But who decides? • Grow wasteful.ng sugarcane in a water short area may be wasteful, and a planner may feel that less water intensive crops will save water. But, the individual farmers, who are the decision-makers, may not agree.
Saving Evaporation-Transpiration â€˘ Which are the candidates for saving? Item
No good and cheap techniques
Evaporation from Waterlogged Area
Reducing seepage Reuse or recycling of drainage
Wet Soil Evaporation
Sprinklers do not achieve this. Drips do, but only whe crop canopy does not cover the whole area Mulches or plastic covers on land between crop seasons wil be of use 8
Saving Leakage of water â€˘ Externalities are important. â€˘ Canal to Waterlogged Areas to evaporation and transpiration of weeds: Loss of both water and land, and saving is important.(But, are we harming a (new) wetland ecology? â€˘ Canal to GW: A loss if a) if the additional anthropogenic GW or the bae flow from this, is not being used, or b) If the GW is saline and cannot be used, or c) regenerated base flow I near the coast, and cannot be used 9
Saving of leakages (contd) â€˘ Saving canal seepage may allow additional gravity command, whereas mopping this through GW extraction will require energy â€˘ On the other hand, use of additional storage in GW space may overcome, in part, the topographic limitation in creating surface storages.
Likely Responses to water Savings Measure
Public Canal Manager- If he faces shortages in the downstream Canal Water User-If he has volumetric allocation and excess land to use the saved water
Those who reuse the seepage. The canal water user also may be in this category
Better distribution at branchings
Changing to crops producing more per unit water ET
Are there such crops? Farmers gain will decide
Mopping leakage, leading to non-beneficial ET, for reuse
Project Manager-If he gets the water Waterlogged area farmers
None But thoes who do not benefit may have little interest
How Much Water Can be Saved? ??
Published on Apr 22, 2013