A New Conceptual Framework for Water Conservation Based on Addressing Water Balance, Crop Rotation and Economics

Transcription

1 6-7 December, 204, Riyadh, Saudi Arabia A New Conceptual Framework for Water Conservation Based on Addressing Water Balance, Crop Rotation and Economics A.Z. El-Bably, S.A. Abd El-Hafez, M.A. Mahmoud and Samiha A.H. Oud Soil, Water and Environment Research Institute, Agric. Res. Centre, Giza, Egypt Abstract: This paper presents a conceptual framework for water conservation where, new concepts are introduced and new indicators for describing e status of irrigation management defined. The new performance indicators are systematically tied to e very important and related issues of crop rotations, water balance and economics. The concepts and indicators in is paper are expected to be instrumental among oer ings in: ) The identification of opportunities for water savings and increasing water productivity; 2) Developing a better understanding of present patterns of water use and impacts of interventions. The framework can be adapted to specific farm conditions. Using a case study of two successive rotations since 202, in Kafr El- Sheikh- Egypt, we demonstrate how e new performance indicators can be used to develop better understanding of e reality governing current irrigation water taking into account e difference in e yield and value of different crops. Analysis results show at net inflow and depletion in e Rice-Sugar beet-cotton- Wheat (RSCW) rotation system are 3883 mm and 25 mm respectively, which are higher an at of e corresponding figures (3765 mm and 229 mm respectively) in Cotton-Wheat Rice-Wheat (CWRW) rotation system. The gross and net depletion fractions (DF) are 6. and 6.2% less in e CWRW compared wi RSCW. Net inflow of rice was 520 mm greater following cotton and sugar beet an wheat in RSCW and wheat in CWRW. Total outflow was higher in RSCW an CWRW (323vs. 22 mm). The RSCW rotation has e highest net returns, about US$2286 ha compared wi US$2003 ha for a CWRW rotation. Therefore, when water is becoming a limiting factor for agriculture, a systems performance indicator raer an a crop performance indicator is needed to determine e optimum crop rotation, water allocation among ose crops and ultimate net return of e cropping system should be. Key words: Irrigation water Performance indicators fraction Crop rotation and economics INTRODUCTION The study aimed to raise awareness of e seriousness of e water scarcity issues in e region and about e urgent needs and commitments for regular assessment and monitoring of e current status of water-use efficiency in order to identify practical ways of improving water-use efficiency at e farm levels, as well as in e agriculture sector at large, wi a focus at participatory approaches. The study tackled issues such as e challenges of water scarcity in agriculture; conceptual issues in water productivity and water-use efficiency and country-specific experiences wi a focus on policies enacted, innovations introduced, good practices and improving on-farm water use efficiency wi e active participation of stakeholders. The study concluded wi e expectation at water accounting and provides generic terminologies and procedures approaches in e field in order to improve on-farm water- use efficiency and ensure a positive impact in eir respective countries. Due to vastly different types and scales of use, communicating about water between professionals and non-water professionals is quite difficult. Policy decisions are often taken wiout a clear understanding of consequences on all water users. As competition for a limited supply of water increases, it becomes increasingly important to clearly communicate about how water is being used and how water resource developments will affect present use patterns. As irrigation is a large consumer of water, developments in irrigation have profound impacts on farm-wide water use and availability. Yet, planning and execution of on-farm irrigation interventions often take place wiout consideration of Corresponding Auor: A.Z. El-Bably, Soil, Water and Environment Research Institute, Agric. Res. Centre, Giza, Egypt. 35

2 oer uses. One of e main reasons for is restricted According to ICARDA trials and farmers view of irrigation workers is inadequate means to describe demonstration fields in Syria, a cubic meter of water used how irrigation water is being used. On-farm irrigation in SI produced, on average, an extra 3 kg of wheat over efficiency is e most commonly used term to describe rainfed yield (WUE 3 kg m ), whereas a cubic meter how well water is being used. But increases in irrigation used in FI produces about 0.5 kg, i.e., WUE 0.5 kg m. efficiency do not always coincide wi increases in overall This large difference in e WUE is attributed to e basin productivity of water. conjunctive use of rainfall and SI water. In Jordan rainfall One of e most extensively used terms to evaluate WUE in rainfed wheat in Mushagar (300 mm annual e performance of an irrigation system is water rainfall) is 0.33 kg m, when e cubic meter of rainfall is efficiency. In general terms, water efficiency is defined as 3 combined wi ½ m supplemental irrigation, e overall e ratio between e amount of water at is used for an WUE was increased to 3.5 kg m. Wi such obvious intended purpose and e total amount of water input advantages decision makers at e national level may wiin a spatial domain of interest. need to consider e feasibility of diverting some In is context, e amount of water applied to a field irrigation water from FI to SI, or a combined use of bo of interest but not used for e intended purpose is a for optimal crop-water allocation [5]. loss from at field. Clearly, to increase e efficiency of Average WUE of rain in producing wheat in e dry a field of interest, it is important to identify losses and areas of West Asia and Nor Africa (WANA) is about minimize em. Depending on e intended purpose and 0.35 kg grain m, alough wi good management and e field of interest, many efficiency concepts are favorable rainfall (amount and distribution), is can be involved, such as crop water use efficiency, water- increased to kg grain m. However, water used in SI can application efficiency and oers []. be much more efficient. Research at ICARDA showed at During e crop grow period, e amount of water a cubic meter of water applied at e right time (when e usually applied to e field is much more an e actual crop is suffering from moisture stress), combined wi field requirement. This leads to a high amount of surface good management, could produce more an 2.5 kg of runoff and seepage and percolation. Seepage and grain over e rain-fed production. This extremely high percolation account for about 23-40% of e total water WUE is mainly attributed to e effectiveness of a small input to e field [2, 3]. amount of water in alleviating severe moisture stress On-farm productivity of irrigation water can be during e most sensitive stage of crop grow and seedincreased by doing one of e following: () increasing filling. When SI water is applied before such conditions yield per unit evapotranspiration during crop grow; (2) occur, e plant may reach its high yield potential [6]. In reducing evaporation especially during land preparation; comparison to e productivity of water in fully irrigated (3) reducing seepage and percolation during land areas (when rainfall effect is negligible), e productivity preparation and crop grow periods; and (4) reducing is higher wi SI. In fully irrigated areas wi good surface runoff. management, wheat grain yield is about 6t/ha using 800 Define water productivity (WP), using e first of e mm of water. Thus, e WUE is about 0.75 kg m, oneabove definitions, as e ratio of e physical yield of a ird of at is under SI wi similar management. This crop and e amount of water consumed, including bo suggests at water resources may be better allocated to rainfall and supplemental irrigation. Yield is expressed as SI when oer physical and economic conditions are a mass (kg or ton) and e amount of water as a volume favorable. 3 (m ) [4]. In e Beni-Sweif area of Egypt, Surface water is e Water is likely to be e single most important main source of irrigation for all farmers in e survey. regional and global resource issue in e coming years. Its Main produced crops are wheat and berseem for winter wise use is becoming an immediate necessity. A cropping, whereas, summer cropping includes cotton, criterion at perhaps is generally accepted to evaluate a sunflower, tomatoes and corn. On-farm WUE is e wise use of water is what is referred to as Water Use highest for cotton (0.75), berseem and corn (0.72, each), Efficiency (WUE). The term indicates how much food indicating at actual water use exceeds water and/or fiber a cubic meter of water may produce. requirements by about 25 to 28%. The lowest WUE of 0.56 Comparing WUE of Supplemental Irrigation (SI) of wheat for tomatoes suggests at producers over-irrigate is wi at of Full Irrigation (FI), a real opportunity for water crop by 44% compared to its requirements. Therefore, any use improvement was found. improvement in e water-use efficiency of is crop will 36

3 save a large amount of scarce water at can be used to expand e farm s irrigated area or for oer crops. Likewise, farmers of wheat and sunflower exceed crops water requirements by 35%. Eier below-average yields or inefficient use of irrigation water can explain ese low ratios of on-farm WUE for tomatoes, wheat and sunflower. The survey also confirms at wheat plays an important role in farmers crop rotations. The most common winter summer rotations are wheat rice (20% of e cultivated area), berseem (clover) cotton (2%), wheat maize (0%) and berseem maize (8%). Four-fifs of e wheat farmers in Egypt grow wheat every year. Wheat farmers devote one-half of eir winter cropland (or slightly less an one quarter of eir total sown area) to wheat. In terms of e value of production, e most important crops grown by wheat farmers are cotton (24% of e total), wheat (9%) and rice (5%). Cotton, fruits and vegetables account for a larger share of e value of production an of area because value per hectare is higher an for staple foods. The objectives of is paper are to present concepts and definitions necessary to account for water use, depletion and productivity. The accounting procedures and standards given here are designed to be universally applicable for evaluating water management wiin and among all sectors. A goal of is approach is to develop ) The terminology and a procedure at can be applied to describe e present status and consequences of water resources related actions carried out in agriculture and oer water sectors; 2) Examples of water accounting at two levels of rotations to test and demonstrate e utility of e meodology; and to determine which scheme can achieve e highest yields compared to e amount of water applied while maximizing profit. Levels of Analysis: Agricultural researchers often focus on a field level or a plot level dealing wi crop varieties and farm management practices. Irrigation specialists focus on a set of fields tied togeer by common resource water. On-farm irrigation specialists are concerned wi oer uses of water in agriculture and extension. A perceived improvement in water use at e farm level may improve overall productivity of water in a basin, or it may reduce productivity of downstream users. Only when e intervention is placed in e context of a larger scale of analysis can e answer be known. Similarly, basin-wide studies may reveal general concepts about how water can be saved or productivity of water increased, but field level information on how to achieve savings or increase water productivity is required. Therefore, micro level of water use in agriculture is defined for which water accounting procedures are developed: Micro Level: Use level, such as an agricultural field, a household, or an environmental use. The water accounting meodology is developed in a manner such at it can be generically used for irrigation, municipal, industrial, environmental, or oer uses of water. But e focus of is paper will be on irrigation services and use of water and emphasis will be on quantities of water at e field and irrigation service levels. In e future phases, concepts and examples will be presented from multiple uses of water and water quality. Water Balance Approach: The water accounting meodology is based on a water balance approach. Water balances consider inflows and outflows from field. Water accounting components at field are inflow, storage change, process depletion, non-process depletion and outflow. The inflow components are irrigation application, rainfall, subsurface contributions and surface seepage flows. Storage change component is soil moisture change in active root zone. Process depletion components are actual evapotranspiration, outflow components are deep percolation, seepage and surface runoff. Estimates of actual crop consumptive use at a regional scale are questionable. And drainage outflows are often not measured, as more emphasis has been placed on knowledge of inflows to irrigation systems. In spite of e limitations, experience has shown at even a gross estimate of water balances for use in water accounting can be quite useful to managers, farmers and researchers. Water Accounting Definitions: The water accounting is to classify water balance components into water use categories at reflect e consequences of human interventions in e hydrologic cycle. Water accounting integrates water balance information wi uses of water. Inflows into e domain are classified into various use categories as defined below. Gross inflow is e total amount of water flowing into e field from rainfall and surface and subsurface sources. Net inflow is e gross inflow plus any changes in storage. If water is removed from storage over e time period of interest, net inflow is greater an gross inflow; if water is added to storage; net inflow is less an gross inflow. Net inflow water is eier depleted, or flows out of e field of interest. 37

4 Balance approaches have been successfully used to has a broader basis an water use efficiency [5], which study water use and productivity at e field level (for relates production of mass to process depletion example, [7, 8, 9, 0, ]). (transpiration or evapotranspiration for irrigated Water depletion is a use or removal of water from agriculture). Here it is defined in terms of net inflow, field at renders it unavailable for furer use. Water depleted water and process depletion. depletion is a key concept for water accounting, as it is often e productivity and e derived benefits per unit of Pr oductivity Netflow inf low water depleted we are interested in. It is extremely (3) important to distinguish water depletion from water diverted to a service or use, because not all water diverted depleted to a use is depleted. Water is depleted by ree generic (4) processes, e first two described by [2, 3]. A ird type of depletion occurs when water is incorporated into a PW PW Pr oductivity Pr oductivity Pr ocess process product. (5) PW The Two Generic Processes Are: The following relationships exist between productivity and water indicators. Transpiration: it is water transpired by crops plus at amount incorporated into plant tissues. PW depleted PW net inflow / DF net (6) Evaporation: water is vaporized from surfaces or transpired by plants For an irrigated service area, ese are external Incorporation into a product: by a process such as indicators of system performance relating e output of incorporation of irrigation water into plant tissues. irrigated agriculture to its main input, water. IIMI s Process depletion is at amount of water diverted external indicators [6, 7] draw from is water and depleted to produce an intended good. For accounting list for a minimum set of indictors and include agriculture, it is water transpired by crops plus at e productivity of water related to process depletion. amount incorporated into plant tissues. Accounting Components at Field Level: The use level Performance indicators for water accounting follow of analysis for irrigation is taken at e field level depleted fraction and effective efficiency concepts are wi inflows and outflows shown in Table. This is presented [3, 4]. e level where crop production takes place e process Water accounting performance indicators are of irrigation. Agricultural research at is level is presented in e form of fractions and in terms of often aimed at increasing productivity per unit of land productivity of water. and water and conserving water. The key question is: Depleted Fraction (DF) is at part of e inflow at Which water? Again, it is important to understand e is depleted by bo process and non-process uses. category of water against which production is being Depleted fraction can be defined in terms of net, gross measured, or e category of water at is being and available water. conserved. At e field level, e magnitudes of e components of e water balance are a function of crop and cultural DFnet NetFlow () practices. Different crops and even different varieties of crops, will transpire water at different rates. Irrigation techniques influence evaporative losses and volumes of DFgross Grossin flow (2) deep percolation and surface runoff. For example, drip irrigation minimizes ese components, while surface Productivity of Water (PW) can eier be related to application induces depletion by evaporation. Also, e e physical mass of production or e economic value of amount of water delivered influences runoff and deep produce per unit volume of water. Productivity of water percolation. Oer cultural practices such as mulching and can be measured against gross or net inflow, depleted crop spacing affect e amount of water stored in e soil water, or process depleted water. Productivity of water and e amount of runoff and deep percolation. 38

5 Table : Field level water accounts in Nor Delta: RSCW rotation. Inflow Rice Sugar beet mm Cotton Wheat Two annuals Irrigation Effective rainfall Subsurface Lateral seepage flows Gross inflow Storage change Net inflow Actual Evapotranspiration (process) Total Outflow Surface runoff Deep percolation Total outflow Performance Depleted Fraction (gross) Delectated Fraction (net) Production (kg ha ) Production per net inflow (kg mm ) Production per total depletion and process (kg mm ) Production per net flow per depletion fraction (net) Irrigation cost in US$ Net return in US$ Table 2: Field level water accounts in Nor Delta: CWRW rotation. Cotton Wheat Rice mm Wheat Two annuals Inflow Irrigation Effective rainfall Subsurface Lateral seepage flows Gross inflow Storage change Net inflow Actual Evapotranspiration (process) Total Outflow Surface runoff Deep percolation Total outflow Performance Depleted Fraction (gross) Delectated Fraction (net) Production (kg ha ) Production per net inflow (kg mm ) Production per total depletion and process (kg mm ) Production per net flow per depletion fraction (net) ` Irrigation cost in US$ Net return in US$

6 Water accounting procedures attempt to capture e 0.70 and 0.63 for rice, sugar beet, cotton and wheat, effects of different crop and cultural practices on how respectively and ey were 0.70, 0.63, 0.55 and 0.63 for water is used and depleted at e field level. cotton, wheat, rice and wheat to a depleted fraction gross At e field level, it is sometimes impossible and (Table 2),. The depleted fraction net of 0.55, 0.8, 0.69 and oftentimes unnecessary to know e fate of outflows. By 0.6 for rice, sugar beet, cotton and wheat, respectively, accounting for water use at e field level, en placing it while ey were 0.69, 0.6, 0.55 and 0.6 for cotton, wheat, in e context of irrigation service and basin levels, it is rice and wheat in e second crop rotation. On a two possible to match field level interventions wi annual basis, e depleted fraction net is quite middle at requirements at e irrigation service level, or water basin 0.65 in e RSCW and 0.6 in CWRW rotations, due to a level, or bo. high amount of evapotranspiration and small amount of A field experiments was conducted during four rainfall in winter season. The depletion fraction of net successive seasons of summer 200, winter 200/20, inflow was, wi an average of 0.65 lower an.0 as a summer 20 and winter 20/202 in farmers' farms of e result of e practice of deficit irrigation used. In is case, command area in Nor Delta. Two cropping rotations evapotranspiration is reported so at productivity per were applied to measure water productivity indicators on total depletion and per process depletion can be crop rotations of wheat. All cropping sequences were calculated. selected as a dominant in Nor Nile Delta region. The water application by crop for winter cropping is. Rice Sugar beet Cotton Wheat (RSCW) 860 mm for sugar beet and 57mm for wheat. For summer cropping, water application, as an average for e sample 2. Cotton Wheat- Rice - Wheat (CWRW) farms, is 952 mm for cotton, 520 mm for rice. Cropping systems evaluated were rice- sugar beet Each year's crop rotation treatments included rice- cotton wheat (RSCW) and cotton wheat- rice - wheat sugar beet cotton wheat (RSCW) and cotton wheat- (CWRW). Net inflow and depletion in RSCW was 3883 rice - wheat (CWRW). RSCW were compared to a two- mm and 25 mm, respectively, greater an CWRW which year cycle of CWRW. The researchers used seeding rates, was 3765 mm, 229 mm, respectively; however, e fertility and pest control practices common in e region. depleted fraction for gross and net decreased by 6. and 6.2% compared wi RSCW. Net inflow of rice was 520 Example of Water Accounting: To illustrate water mm greater following cotton and sugar beet an wheat in accounting, example is chosen from e use levels. RSCW and wheat in CWRW. Total outflow was higher in The use level example is taken from e crop rotations RSCW an CWRW (323 vs. 22 mm). Irrigation cost followed by farmers in Nor Delta in Egypt. was higher (US$486 vs. 45) in RSCW compared to CWRW. The RSCW rotation had e highest net returns, Field-Level Accounting Example: As a field-level example, about US$2286 ha - compared wi US$2003 ha for a results of agricultural trials based on field experiments CWRW rotation. carried out in farmers' farms of e command area in Nor Water productivity according to e defined in Delta in Egypt are reported in a water accounting format technical terms used, is e highest for sugar beet (Table ). In is area, e water duty falls short of compared to wheat in winter cropping and rice compared potential crop requirements as water is scarce relative to to cotton in summer cropping. land. In response, farmers typically have a strategy of Seasonal irrigation water-use efficiency was highest deficit irrigation, or giving less water an e potential in rotation of RSCW and e current status of on-farm crop requirement, us giving em e opportunity to water-use efficiency of wheat under specific farm irrigate more land. conditions in e Kafr El-Sheikh province, norern Delta, Yields were reported as 9.34 tons per hectare for rice, Egypt, where e recent use of irrigation deficit has been tons per hectare for sugar beet, 2.26 tons per hectare expanded to increase wheat production in areas. The for cotton and 8.83 tons per hectare for wheat in RSCW resulting indicators of on-farm water-use efficiency are rotation (Table ). While yields in CWRW rotation were very useful in guiding policies toward improving irrigation 2.4 t ha, 7.7 t ha, 9.84 t ha and 6.35 t ha for efficiency. Improving water-use efficiency to sustain and cotton, wheat rice and wheat, respectively as shown in improve wheat production in Norern Delta, Egypt is Table 2. All of e irrigation and rainfall applied is vital especially at e country has been classified as depleted leading to a depleted fraction gross of 0.55, 0.89, irrigation deficit. 40

7 It is meaningful to compare values of mass of prices for rice might swing e water-value factor in favor production per unit of water diverted or depleted, when of e rice-wheat rotation in e CWRW and RSCW comparing like crops. But when different crops are rotations. compared, mass of output is not as meaningful. There is To obtain e required amount of water to a clear difference between kg of sugar beet and kg of produce e average yield levels, e estimated crop rice produced per mm of water depleted wiin e same water balance are used. This is done by calculating crop rotation of RSCW and between kg of cotton yield e amount of water required for each crop at e and kg of wheat in CWRW rotation. One approach is to mean levels of e independent variables appearing convert yields into value of production using local prices. in at water balance. For winter and summer cropping, A second approach is to use Standardized Gross Value of bo fixed allocatable input model and variable input Production (SGVP). Standardized Gross Value of model are used in estimating e amount of water required Production is used to measure economic productivity to for em. allow comparisons across different agricultural settings Growers depend on several factors such as by using world prices of various crops [6, 7 and 8]. To calculate SGVP, yield of a crop is converted into an equivalent yield of a predominant, traded field crop using local prices. Then is mass of production is converted into a monetary unit using world prices. This investigation has been to create a decision tool wi user interaction to examine crop rotation and limited water allocations wiin land allocation constraints to find optimum net economic returns from ese combinations. This decision aid is for intended producers wi limited water supplies to allocate eir seasonal water resource among a different of crops. But, it may be used by oers proper irrigation meods, good crop rotations and effective marketing to secure e best price for e product. Researchers at Sakha Agricultural Research Station (SARS) in Kafr El-Sheikh, Egypt are conducting long-term, multicrop research at a farm location to define e best irrigation management practices for growers of rice, sugar beet, cotton and wheat crops. They have completed e two year of study to determine e impact on profitability of irrigation, crop rotation and price. For all iterations, net return to land, management and irrigation equipment is calculated: interested in decisions concerning allocating limited water to crops. Decisions are intended as a planning tool for Net return (commodity price X yield) (irrigation cost + production cost) crop selection and season allocations of land and water to where: crop rotations. commodity prices were determined from user inputs, In e various rotations, price determines profitability. crop yields were calculated from yield-irrigation But a rotation of RSCW consistently provides higher relationships based on field research, irrigation costs were profit an CWRW rotation. One of e objectives of is calculated from lift, water flow, water pressure, fuel cost, research is to improve e growers ability to make such pumping hours, repair, maintenance and labor for investment decisions and to provide em wi decision irrigation and production costs were calculated from user aids like Irrigator Pro to better manage irrigation based on inputs. User inputs including water supply, irrigation economics and not simply yields. costs, crop production costs, commodity prices and The survey results also highlight e intensity of maximum crop yields can be tailored to user wheat production in Egypt. Wheat crop in rotation of circumstances. These inputs directly influence e RSCW produce US$643, while in e CWRW rotation, selection of e optimum crop rotation, water allocation wheat crop produce UD$469. Wheat farmer harvests 8.83 among ose crops and ultimate net return of e cropping metric tons of wheat obtained from RSCW rotation. While system. it was 6.35 metric tons of wheat obtained from CWRW rotation. It has been a while since agricultural researchers REFERENCES discovered and en proved e benefits of crop rotation. Since en, most farmers have embraced e practice of. El-Bably, A.Z., M.E. Meleha and A.A. Abd Allah, switching a piece of ground from one crop to anoer to Enhancing water use efficiency, rice improve yields, reduce erosion potential and break insect and disease cycles [9]. We got a higher return for our water wi rotation of RSCW and used its limited water more efficiently an CWRW rotation. Higher market productivity and saving water in Nor Delta, Egypt. rd The 3 International conference on water resources and arid environment at King Fahed Cultural center, Riyadh, KSA, Proc. Water resources, pp:

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