WATER RESOURCES PLANNING MODELING FOR EFFICIENT MANAGEMENT OF IRRIGATION CANAL

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1 Journal of Agricultural, Food and Environmental Sciences UDC Original Scientific Paper WATER RESOURCES PLANNING MODELING FOR EFFICIENT MANAGEMENT OF IRRIGATION CANAL G. Patamanska 1 * Institute of Soil science, Agrotechnologies and Plant Protection, Sofia, Bulgaria *coresponding auor: patamanska_g@yahoo.com Abstract In e last years e spreadsheet-based models are widely applied for water resources planning and management. In is report, a model for planning water allocation from irrigation canal is presented. Algorim based on e water balance which allows for allocation of available water resources of e source according to water requirements of crops in irrigated area, considering current technological constraints was developed and implemented in Excel environment. An existing canal was as a case study. The spreadsheet-based model provides support for efficient management of e irrigation canal. Keywords: irrigation canal, water allocation, planning, spreadsheet-based model Introduction Planning of water allocation in irrigation canals is an important managerial activity aimed efficient use of water for irrigation, minimizing yield losses of e irrigated crops due to water deficit and water stress, also preventing over supply and e negative outcomes such as water logging and salinization agricultural land. Using e optimization meods and computers, e operation of irrigation canals can be planned effectively. Last decades many models based of e integer linear programming and mixed integer linear programming techniques have been developed for solving e problem of optimal water allocation in irrigation canal (Anwar et al., 2001; Ramesh et al., 2009; Sani et al., 2000). By reason of certain limitations in eir formulation few of e developed models were used for water resources planning and management. For practical use, computer implementation of e planning algorims is good to be done in an accessible manner for use of e engineering staff in charge of operational management of irrigation system (Steele et al., 20). An alternative is e software application EXCEL, which as part of Microsoft Office is widespread and required basic computer knowledge. In is paper a model for planning water allocation from run-of-e river irrigation canal is presented. Algorim based on e water balance which allows for allocation of available water resources of e source according to water requirements of crops in irrigated area, considering current technological constraints was developed and implemented in Excel environment. The model was validated for an existing irrigation canal. Material and meods Water delivery network of e most of e existing irrigation systems consists of main canal, which is flowing all irrigation season and distributaries canals, which are controlled periodically for need of delivery of irrigation water to its command area. As water requirements of e agricultural crops are varied in e different grow stages, total of e days of e irrigation season is divided to e equal time intervals, a leng of a week or a decade ( days). Water distribution schedule is prepared on any day during e time interval at enables allocation of available water in terms of actual irrigation water requirements considering e technological constraints. Maematical formulation of e model The planning model works on daily basis and -days irrigation period. As e main canal is feeding variable river discharge, e river flow is measured on any day of e time period. Available net water discharge (daily supply at

2 42 G. Patamanska e head of main canal minus losses in main canal) is allocated to e distributary canals to fulfill eir demands in terms of water for irrigation of e crops. For proper execution of e plan of water supply of manually operated distributary canals, it is essential at e canal operation is to be simple. In e present operation scenario, distributary canals will be running at full, half or nil capacity on every day during e irrigation period. To keep daily water balance in e main canal one of e canals will be running in variable supply (Ramesh et al., 2009). Objective function The objective function is defined as maximization of e total supply to e distributary for e entire irrigation period. Maematical representation of e objective is: Max N k1 i1 il where k = day number, N= distributary canals number, i = e distributary canal number, l = distributary canal wi varied supply number, = daily supply in e l distributary canal on k day (m 3 /s), = daily supply in e i distributary canal on k day(m 3 /s) qi qi distributary is closedon k distributary is half open on k distributary is fully open on k day where q i= capacity of i distributary canal (m 3 /s). In daily allocation of e net available irrigation water at e head of e main canal to e distributaries should be kept e following technological constraints. Main Canal Supply Constraint To ensure e balance of water amounts in e main canal e sum of supplies to distributary on any day should be less an or equal to net daily supply in e main canal: N i1 il v k day day. where vk=net supply in e main canal on k day. Distributary canal demand constraint The sum of daily supply of e distributaries for e irrigation period should be less an or equal to demand for day period. Maematical representation of is constraint is: k1 D i i =1,2,.N And l (3.1) and for e distributary canal wi variable supply: k1 (3.2) D l where D i= demand for i distributary canal for day period (m 3 /s), D l = demand for i distributary canal wi varied supply for day period (m 3 /s). Canal capacity constraint (1) The water supplies to canals should not exceed e capacity of e canals on any day during e time period. i vk q q maxi vmax (4) where vmax= design capacity of e main canal(m 3 /s), q maxi=design capacity of e i distributary canal (m 3 /s). In addition e distributary canal wi variable supply should be supplied discharge at least equal to half design capacity to maintain sufficient flow dep in e canal. This limitation is expressed as follows: q max l q k=1,2,.. (5) max l 2 These equations and constraints constitute a maematical model of plan of supply and distribution of water in irrigation canal. Since an optimization problem is formulated e solution is an optimal water allocation plan which enables water supply of distributaries canals in accordance wi e water requirements of e irrigated crops. In is study an approach to be found in Excel environment an approximate solution for e k=1,2. optimization problem (1)-(5) is adopted. (2)

3 43 G. Patamanska 0 кm Р-1 2 m 3 /s Р-2 4,2 m 3 /s Р-2-1 ГВ-2 1,5 m 3 /s ГВ-4 1 m 3 /s ГВ-5 2,2 m 3 /s Legend: Р - Irrigation canal ГВ - Conduit Figure 1. Layoutof e main canal of "Stryama-Chirpan Irrigation system Results and discussion The spreadsheet model for operational planning of supply and distribution of water was developed and validated wi data main canal "Stryama-Chirpan" irrigation system (Figure 1). The water source for is irrigation system is e Stryama River. The main canal works during e irrigation season from May to October and irrigates 1,843 ha agricultural area planted wi rice, corn and vegetables. The canal has five distributaries. Water for rice fields is supplied by two open canals. Three conduits are located on e canal course. Details of e distributaries have been given in Figure 1. The proposed algorim based on e water balance was built in is table using Excel capabilities for consecutive estimates and available logic functions. No Visual Basic macros were used for e model development in Excel environment. The only macro was designed to reset e table before any new estimate us provides an opportunity for repeated use of e table. The spreadsheet layout is shown on Figure 2.

4 44 G. Patamanska Figure 2.Spreadsheet layout for planning of water allocation from main canal of "Stryama-Chirpan Irrigation system. The input data needed to start e calculations are daily river discharge, minimum river flow rate, canal losses, demands of e distributaries canals for day period (m 3 /s), defined on e basis of net irrigated norms of irrigated crops. Input data are entered in e boxes from e table, colored in purple. The net supply values at e head of e main canal for any days of e irrigation period are located in e ird column of e table. In e next columns each of e distribution canals has a box in which e values of supply for each day of e interval are entered. The head cell of is box contains maximum capacity of e distributary. Preparation of e water allocation plan For each day of e period initially e daily measured value of river discharge is entered and on its basis e net daily supply at e head of e main canal is calculated as e difference of measured river discharge minus e sum of e amount of canal losses and e minimum river flow rate. Then selection of e operational discharges of distributary canals is made. When entering a value of operational discharge of a distributary canal, e water balance in e main channel is monitored from e result in e cell in e last column of e table "Canal Outflow ". In obtaining a negative result, e supply to e canal should be reduced or stopped. Based on e entries of distributary canals on any day of e period, water discharge value of e distributary canal P-1, which is assumed to operate at variable supply is automatically calculated from e water balance equation and in accordance wi e restrictions (2) - (5). Implementation of e target (1) is monitored by calculating e deviation of water delivery to each distributary from e requested. The model was tested wi data for flow of e Stryama River for e lastten days of June. At e beginning of e period e flow rate of e river is high 8- m 3 /s, but in e last days e main canal can be supplied less water discharge 5.3 m 3 /s The model shows how to manage distributaries in e -day period to fulfill e requests. Request of e canal P-2 is satisfied, t runs at maximum capacity during e irrigation period. Request of conduits ГВ-2, ГВ-4 и ГВ-5 are met for 3consecutive days at work at half capacity. The obtained delivery schedule for e canal wi a variable supply is shown on Figure 3. Its implementation does not require frequent changes of e regulating structure at its head. Total, e accuracy of

5 45 G. Patamanska meeting e requests of canals is relatively high - 4.9%. For e conduits e deviations are greater. This is due to e fact at e canals are oversized relative to e actual needs of e water for irrigation. Also, assuming at e distributaries work completely open or half capacity brings approach in determining e solution of e problem for optimal operational planning. Figure 3. Delivery schedule for e canal wi a variable supply It is appropriate to choose e days at water will be delivered in e canals at do not work continuously close to e dates for watering e crops cultivated in e command area of e distributary. In order to minimize operational losses of e water is also appropriate to adopt operational sequence of distributaries canals "down-up" as e water supply to e canal up stream can immediately begin after stopping e supply of canal downstream. Conclusions The main objective of e modeling in is study is daily allocation of e net available irrigation water at e head of e main canal to e distributaries in accordance wi water requirements and technological constraints. The model developed was validated for existing irrigation canal. Its use for preparation a schedule for distribution and supply of water in e irrigation canal does not create particular difficulties and satisfactory results were obtained. The spreadsheet-based model can provide support for efficient management of e irrigation canal. Ramesh R., Venugopal K., Karunakaran K. (2009).Zero One-programming model for Daily Operation Scheduling of Irrigation Canal, Journal of Agricultural Science, 1(1). Sani C., Pundaranan V.N. (2000). A New Planning Model for Canal Scheduling of Rotational Irrigation. Agricultural Water Management, Vol. 43, pp Steele, D.D., Scherer T.F., Hopkins D.G., Tuscherer S.R., Wright J. (20).Spread shee timplementation of irrigation scheduling by e checkbook meod for Nor Dakota and Minnesota. Appl. Engr. Agric.26(6) pp References Anwar A., Clarke D., (2001). Irrigation Scheduling Using Mixed-Integer Linear Programming, Journal of Irrigation and Drainage Engineering, 127(2), pp