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Improving Water and Land Management for Efficient The 19th ICID Congress, Beijing, Sept. 2005 Q52. IMPROVING WATER AND LAND MANAGEMENT FOR INCREASING EFFICIENCY IN IRRIGATED AGRICULTURE IMPROVING WATER AND LAND MANAGEMENT FOR EFFICIENT WATER USE Q52.1: On-farm water and soil management; IN IRRIGATED AGRICULTURE Q52.2: Performance evaluation and integrated management of irrigation and drainage systems; Luis S. Pereira Q52.3: Conjunctive use of water to optimize food production; Vice-president Hon., ICID Q52.4: Policy options for water saving in irrigation; President, CIGR Q52.5: Management transfer and participatory irrigation and drainage management; Technical University of Lisbon Q52.6: Application of information technology in irrigation and drainage management. For millennia, civilisations developed in water scarce environments. The respective cultural skills are an essential heritage of those nations and peoples, and the humanity as well. A water economic culture is now following a technical one, imposed when the large irrigation schemes were built. Both are generally imported from different cultural and instituttional environments. Management faces therefore difficult challenges due to the fact that irrigators have a perception of problems, practices and objectives different from the non-farmer managers. However, progress in XX century questioned the traditional know-how, which has been often replaced by modern technologies and management Tozeur imported from different environments and cultures. Pressures about water use in irrigation are coming from a ever A turn in viewing traditional growing urban society that understands less and less the rural irrigation is starting in the world and, mainly, the peasants. Most common include: non-technical media ¾“decrease water consumption” - when it should be said “control water demand” Farmers may not have access to other and better technologies, and may do not know how to improve those they are using after centuries But we need to help providing our know-how accepting Oasis of Turpan, farmers cultures and perception Xinjiang 1 Reducing the demand for supplemental irrigation of cereals may However for crops having a high demand for water such as summer crops, be feasible if to decreasing Gross Margins per unit land (GM/ha) including if they have a favourable ratio between yield price and water cost, correspond increased GM per unit water. e.g. tomato in Tunisia, when GM/ha decreases due to less water application The farmer incomes then reduces but, when water is lacking, that the GM/m3 do not increase. It is then questionable to adopt deficit irrigation income is higher than reducing the cropped area. More knowledge about water-yield-revenues is required before adocating deficit irrigation for demand reduction 5000 0.8 GM/ha 3 ) GM/m ) 3 4000 0.6 ha / D 3000 S 0.4 U ( 2000 M GM (USD / m G 0.2 1000 0 0.0 240 320 400 480 560 640 720 800 880 240 320 400 480 560 640 720 800 880 (6) (8) (10) (12) (14) (16) (18) (20) (22) (6) (8) (10) (12) (14) (16) (18) (20) (22) Season irrigation (mm) Season irrigation (mm) Number of irrigations Number of irrigations Zairi et al., 2003 r average ( ), high ( ) and very high ( ) demand conditions Zairi et al., 2003 ¾“pay the full costs of water”, but, … Impacts of water prices on water demand (and irrigated cropped area) at system level what about yield prices and farmers revenues? what about the externalities of irrigation such as Traditional irrigation, Duero Modern irrigation, Guadalquivir aquifer recharge and flood control? Paddies in the Po Valley, courtesy by M. Greppi Impacts of water prices on If multifunctions of irrigated water demand, cropping agriculture are recognized, pattern and income at farm the water is “fully” valued level, Alentejo, Portugal and farmers will pay what is socially and economically acceptable Japan. Inst. Irrig. Drain., 2003 Mitsubishi Res. Inst., 2001 If water is to be paid in full as an economic good the demand will decrease together with the irrigated area and farm income Pinheiro and Saraiva, 2002 2 The depth of applied water D depends upon the technologies ¾ “improve irrigation efficiency”, but available. Improving them to achieve an high uniformity UC that provides for making D close to Dopt relates to the relationship farmers generally know they need to apply water in excess to leach salts, to store water in the soil when deliveries are not between the price of the yield commodity (PY) and the cost of reliable, or to overcome the distribution uniformity of the system the water (PW) New developed oasis near Tozeur, Tunisia Mantovani, 1993 Maximing Yields or maximizing WP follow different objectives which relate to the socio economic farming conditions ¾“more crop per drop”, or “increase water productivity”. However, this may be achieved by improving agronomic practices not decreasing water use Moreover, a peasant farmer, having 0.5 ha/family, do not understand the water productivity concept: he needs to increase land not water productivity, because it relates to the revenue he may get from his land Qingtongxia, Ningxia Molden at al., 2003 There is a contradiction between water and land productivity A key issue is to know the relationship between “applied water” that is solved differently by and “costs” and “revenues”, maily these ones! a water manager Max(WP) a farmer Max(LP) English et al., 2002 3 The farm’s socio economic Where this water goes? To irrigation only? conditions dictate options that may be different of those of water managers May be it is worthwhile to adopt new water use concepts Max net income for commercial farming Is below max Yield (near max WP) Max total income for small (family) farmers Is near max Yield (far from max WP) Tank irrigation in Sigirya, Sri Lanka WATER USE WATER USE = Diverted for any purpose CONSUMED NON- FRACTION CONSUMED FRACTION CONSUMED NON- Preserved Degraded FRACTION CONSUMED Quality Quality FRACTION NON- REUSABLE Preserved Degraded REUSABLE Quality Quality Beneficial NON- Non-beneficial (waste) Non-beneficial REUSABLE REUSABLE Non- LOSSES beneficial A new approach looking the Basin and not the irrigated fields Pathways to improve water use alone has been developed by IWMI along these lines WATER USE ¾Identify the water pathways CONSUMED NON- FRACTION CONSUMED FRACTION Preserved Degraded Quality Quality ¾Maximize beneficial uses NON- REUSABLE REUSABLE Beneficial Waste ¾Minimize non-beneficial uses Non- LOSSES beneficial ¾Control, avoid water losses 4 Effective rain WATER DIVERSION Effective rain WATER DIVERSION Environment Agriculture Agriculture Domestic Industry and other and landscape Conveyance + Seepage + Classical transport & Conveyance + Seepage + distribution runoff distribution runoff distribution efficiency Total WP Irrig WP reuse Non-crop ET reuse Non-crop ET Classical application Application to Percolation + efficiency Application to Percolation + cropped field runoff cropped field runoff Farm WP Transpiration Soil evapor Transpiration Soil evapor WUE YIELD YIELD WATER DIVERSION WATER DIVERSION AGRICULTURE AGRICULTURE Reservoir Evaporation Reservoir Evaporation System Seepage + runoff System Seepage + runoff N-BWU BWU Percolation + Field N-BWU runoff Percolation + Leaching BWU Field runoff Non-crop ET Leaching Crop ET Non-crop ET YIELD Crop ET NCF CF CF NCNRF NCRF YIELD WATER DIVERSION Pathways to improve water use WATER USE Agriculture Environment Urban Industry (and landscape) and other ¾Identify the water pathways CONSUMED NON- FRACTION CONSUMED treatment FRACTION Preserved Degraded Quality Network Non-consum Non-consum Consump Quality NON- Seepage + runoff Reusable Non-reusable use REUSABLE REUSABLE Beneficial Non-beneficial use Reuse Waste Field Non- LOSSES Beneficial + non-benef. use beneficial Runoff + percol Maximized beneficial uses Non-reuse Reusable Wastes Losses Cons.use Minimized non-beneficial uses Wild ET Crop ET Leaching Controlled, avoided water losses Efficient water use Losses Wastes Beneficial use High water productivity 5 On farm water management for efficient water use Modern sprinklers may produce excellent performances in set Objective Technology systems, ... Reduce demand • Select low demand crop varieties/crop patterns • Adopt deficit irrigation if design is adequate Water saving • Improve irrigation systems and the selected system uniformity and management is appropriate for the • Reuse water spills and runoff local environmental Water conservation • Soil management/surface constraints and farming mulch conditions Higher yields per unit of • Adopt best farming practices water • Avoid crop stress at critical periods Higher farmer income • Select cash crops • Adopt appropriate irrigation technologies The same applies When micro-irrigation – drip, SDI, micro-sprinkling - to moving gun are well designed and managed, performances can sprinklers under be excellent, but … non-windy conditions ... these are not achievable without appropriate support to farmers ... and to the modern sprinklers in moving laterals. They produce excellent performances with low energy when design and management fit the environmental constraints Excellent performances may be achieved with surface irrigation when land levelling and irrigation technologies are appropriate The challenge is to pay adequate attention and provide incentives to support farmers in improving their systems Adopting zigzag furrowing, shortening the basin strips and using a PE pipe and valved tubing available in the market, this farmer reduced the demand from about 1500 to near 1000 mm. But DU still is very low because land is unlevelled!
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