Modern analysis of surface irrigation systems with WinSRFR

WinSRFR is a new generation of software for analyzing surface irrigation systems. Founded on an unsteady flow hydraulic model, the software integrates event analysis, design, and operational analysis functionalities, in addition to simulation. This paper provides an overview of functionalities, interface, and architectural elements of the software, and discusses technical enhancements in version 2.1, released in late 2007, and version 3.1, scheduled for release in 2009.     

Seasonal on-farm irrigation performance in the Ebro basin (Spain): Crops and irrigation systems

Irrigation performance assessments are required for hydrological planning and as a first step to improve water management. The objective of this work was to assess seasonal on-farm irrigation performance in the Ebro basin of Spain (0.8 million ha of irrigated land). The study was designed to address the differences between crops and irrigation systems using irrigation district data. Information was only available in districts located in large irrigation projects, accounting for 58% of the irrigated area in the basin. A total of 1617 records of plot water application (covering 10,475 ha) were obtained in the basin. Average net irrigation requirements (IR_n) ranged from 2683 m³ ha⁻¹ in regulated deficit irrigation (RDI) vineyards to 9517 m³ ha⁻¹ in rice. Average irrigation water application ranged from 1491 m³ ha⁻¹ in vineyards to 11,404 m³ ha⁻¹ in rice. The annual relative irrigation supply index (ARIS) showed an overall average of 1.08. Variability in ARIS was large, with an overall standard deviation of 0.40. Crop ARIS ranged between 0.46 and 1.30. Regarding irrigation systems, surface, solid-set sprinkler and drip irrigated plots presented average ARIS values of 1.41, 1.16 and 0.65, respectively. Technical and economic water productivities were determined for the main crops and irrigation systems in the Aragón region. Rice and sunflower showed the lowest productivities. Under the local technological and economic constraints, farmers use water cautiously and obtain reasonable (yet very variable) productivities.     

Effects of water infiltration and storage in cultivated soil on surface irrigation

Surface irrigation analysis and design require the knowledge of the variation of the cumulative infiltration water Z (L) (per unit area) into the soil as a function of the infiltration time t (T). The purpose of this study is to evaluate water infiltration and storage under surface irrigation in an alluvial clay soil cultivated with grape yield, and to determine if partially wetted furrow irrigation has more efficient water storage and infiltration than traditional border irrigation. The two irrigation components considered were wet (WT) and dry (DT) treatments, at which water applied when available soil water reached 65% and 50%, and the traditional border irrigation control. Empirical power form equations were obtained for measured advance and recession times along the furrow length during the irrigation stages of advance, storage, depletion and recession. The infiltration (cumulative depth, Z and rate, I) was functioned to opportunity time (t_o) in minute for WT and DT treatments as: Z_WT = 0.528 t_o^0.6, Z_DT = 1.2 t_o^0.501, I_WT = 19 t_o^−0.4, and I_DT = 36 t_o^−0.498. The irrigation efficiency and soil water distribution have been evaluated using linear distribution and relative schedule depth. Coefficient of variation (CV) was 5.2 and 9.5% for WT and DT under furrow irrigation system comparing with 7.8% in border, respectively. Water was deeply percolated as 11.88 and 19.2% for wet and dry furrow treatments, respectively, compared with 12.8% for control, with no deficit in the irrigated area. Partially wetted furrow irrigation had greater water-efficiency and grape yield than both dry furrow and traditional border irrigations, where application efficiency achieved as 88.1% for wet furrow irrigation that achieved high grape fruit yield (30.71 Mg/ha) and water use efficiency 11.9 kg/m³.     

Farmers’ scheduling patterns in on-demand pressurized irrigation

Irrigation scheduling results from the irrigator's integration of meteorological, environmental and crop information. In this paper, the irrigation scheduling patterns of a group of irrigators in the Candasnos Water Users Association (WUA), located in north-eastern Spain, were analysed. Scheduling sprinkler and drip irrigation in this WUA shows additional complications due to the sharing of a collective pressurized irrigation network and to the need to file water orders two days in advance of its foreseen use. The database created by a remote surveillance and control system was mined to obtain the time evolution of hydrant operation time during the 2004–2008 irrigation seasons. Records were selected for clearly identified crops and irrigation systems, and for verified water allocations. Hydrant operation showed a relationship with meteorology (precipitation, wind speed, relative humidity and air temperature), although this relationship was often not evident when hydrants were individually analysed. Statistical analyses were run to classify irrigator's scheduling practices, leading to the establishment of ten different groups. The adopted classification criteria included the average number of weekly irrigations, the SD of the number of weekly irrigations and the modal range of the irrigation starting time. The irrigation pattern was determined by the irrigator (56%), the irrigation system (33%), and the crop (11%). Only in a fraction of the cases (22%) the time change in the scheduling pattern responded to a clear time trend; in 39% of the cases, changes in time appeared random. Further, 45% of the irrigators used the same irrigation pattern in at least half of their hydrant-years, independently of the crop. Only 14% of the irrigators applied different irrigation scheduling patterns to different crops. Our results suggest that irrigators do not find value or do not have the capacity to develop irrigation patterns more consistent and adapted to the local environment, the crops and the irrigation systems.     

Comparative analysis of main on-farm irrigation systems in Portugal

Traditional irrigation systems still cover a large area of irrigated lands in Portugal. The needs for competitiveness leads to the gradual abandon of traditional systems, resulting in social and economic impacts. Pressurised on-farm irrigation systems provide labour savings but imply important investments. Surface irrigation does not require expensive equipment and is low energy and low labour consuming, if modern systems are implemented. Flexible-pipe, gated-pipe, surge-flow valve and cablegation are the main equipment issues available to Portuguese farmers for modern surface irrigation practice. Conditions for application of these systems have been studied relative to different soil and topographic conditions. Plane land, either horizontal or sloped and undulated fields can be irrigated by surface systems, if a convenient design is accomplished. The adequacy of the irrigation systems has been evaluated and a cost-benefit study was carried out. A case study of a situation with undulated land, representative of South Portugal, is presented in this paper, comparing surface irrigation issues and a sprinkler system. Conclusions show a particular economic interest on adopting surge-valve, gated-pipe and cablegation.     

Basin irrigation design with longitudinal slope

The aims of this paper are to analyze theoretically the influence of the longitudinal slope of a surface irrigation field on the uniformity of irrigation and to provide practical tools to design, analyze and manage surface irrigation systems with longitudinal slope and blocked end. An example is shown where a 20% savings in water is obtained by giving the field the optimal slope.In 1982, Clemmens and Dedrick published a practical set of dimensionless graphs to level-basin design and analysis (with no slope). This article generalizes those graphs taking account the existence of field slope. So, Clemmens and Dedrick's graphs are a particular case of obtained results.The analysis is based on solving one-dimensional free surface Saint-Venant equations including infiltration, applying the dimensional analysis to reduce the number of variables involved. Saint-Venant equations are solved with the finite differences method, applying the full hydrodynamic model and the zero-inertia model. Two computer programs are used: WinSRFR and POZAL (a specific software that calculates the optimal cutoff time).The result is a set of three-dimensional graphs that show the relationships of field slope, irrigation uniformity and the rest of the involved dimensionless variables, related to infiltration parameters, Manning roughness coefficient, cutoff time, inflow rate and field length and width. The graphs could be useful in practice to determine the optimal slope of a field, the inflow rate or the length and width of a field, achieving substantial savings of water in surface irrigation.     

On-farm labour allocation and irrigation water use: case studies among smallholder systems in arid regions

On-farm measurements and observations of water flow, water costs and irrigation labour inputs at the individual parcel level were made in case studies of smallholder irrigation systems in sub-Saharan Africa and south-eastern Arabia. The systems, in which the water source supplied either single or multiple users, were analysed to address the fundamental issues of labour allocation for on-farm water management as this has important consequences for the success of such systems. Results show that the costs associated with accessing water influenced labour input, because when they were low the farmers tended to increase the irrigation rate and reduce the amount of time they spent distributing the water within their parcels. Conversely when water costs were high, lower flow rates and more time spent in water distribution were observed, and this resulted in more uniform irrigation and higher irrigation efficiency. Also, opportunities and demands for farmers to use their labour for activities other than irrigation can lead them to modify operational or physical aspects of the system so that they can reduce the time they spend distributing water within the parcels, particularly when the water is relatively cheap. Awareness and better understanding of how farmers may allocate their labour for water management will lead to more effective planning, design and management of smallholder irrigation systems.     

The effects of irrigation methods with effluent and irrigation scheduling on water use efficiency and corn yields in an arid region

A great challenge for the agricultural sector is to produce more food from less water, particularly in arid and semi-arid regions which suffer from water scarcity. A study was conducted to evaluate the effect of three irrigation methods, using effluent versus fresh water, on water savings, yields and irrigation water use efficiency (IWUE). The irrigation scheduling was based on soil moisture and rooting depth monitoring. The experimental design was a split plot with three main treatments, namely subsurface drip (SSD), surface drip (SD) and furrow irrigation (FI) and two sub-treatments effluent and fresh water, which were applied with three replications. The experiment was conducted at the Marvdasht city (Southern Iran) wastewater treatment plant during 2005 and 2006. The experimental results indicated that the average water applied in the irrigation treatments with monitoring was much less than that using the conventional irrigation method (using furrows but based on a constant irrigation interval, without moisture monitoring). The maximum water saving was obtained using SSD with 5907 m³ ha⁻¹ water applied, and the minimum water saving was obtained using FI with 6822 m³ ha⁻¹. The predicted irrigation water requirements using the Penman-Monteith equation (considering 85% irrigation efficiency for the FI method) was 10,743 m³ ha⁻¹. The pressure irrigation systems (SSD and SD) led to a greater yield compared to the surface method (FI). The highest yield (12.11 × 10³ kg ha⁻¹) was obtained with SSD and the lowest was obtained with the FI method (9.75 × 10³ kg ha⁻¹). The irrigation methods indicated a highly significant difference in irrigation water use efficiency. The maximum IWUE was obtained with the SSD (2.12 kg m⁻³) and the minimum was obtained with the FI method (1.43 kg m⁻³). Irrigation with effluent led to a greater IWUE compared to fresh water, but the difference was not statistically significant.     

Modernization of irrigation systems: A case of research,oriented to improve management

In recent years, the traditional concept of an irrigation project has been changing. From just a physical structure for the storage, conveyance and distribution of water, it is now being regarded as a more complex system, including farmers' participation. This implies an improved management in all phases, from reservoir operation to farm management, and therefore the change from simple operation and maintenance to operation, maintenance and management.To face this new challenge, existing projects must be modernized. The Sorraia Irrigation Project is one of those projects. In this paper major problems are identified and it is showed how research (namely through modelling) can be oriented towards an improved management, regarding the conveyance and distribution systems as well as the on-farm systems.Finally it becomes evident that beyond the technical problems to be solved, the involvement and participation of farmers must be improved at all levels of management. Hence, there is also a need for implementing programs on education, training and extension.     

A distributed agro-hydrological model for irrigation water demand assessment

The actual irrigation water demand in a district in Sicily (Italy) was assessed by the spatially distributed agro-hydrological model SIMODIS (SImulation and Management of On-Demand Irrigation Systems). For each element with homogeneous crop and soil conditions, in which the considered area can be divided, the model numerically solves the one-dimensional water flow equation with vegetation parameters derived from Earth Observation data. In SIMODIS, the irrigation scheduling is set by means of two parameters: the threshold value of soil water pressure head in the root zone, h_m, and the fraction of soil water deficit to be re-filled, Δ. This study investigated the possibility of identifying a couple of irrigation parameters (h_m, Δ) which allowed to reproduce the actual irrigation water demand, given that the study area was adequately characterized with regard to the spatial distribution of the soil hydraulic properties and the vegetation conditions throughout the irrigation season. The spatial distribution of the soil and vegetation properties of the study area, covering an irrigation district of approximately 800 ha, was accurately characterized during the summer of 2002. The soil hydraulic properties were identified by an intensive undisturbed soil sampling, while the vegetation cover was characterized in terms of leaf area index, surface albedo and fractional soil cover by analysing multispectral LandSat TM imageries. Irrigation volumes were monitored at parcel scale.A reference scenario with h_m = −700 cm and Δ = 50% (corresponding to a mean actual to potential transpiration ratio of 0.95) allowed to reproduce the spatial and temporal distribution of the actual irrigation demand at the district scale. The spatial variability of the crop conditions in the considered area had much more influence to assess the irrigation water demand than the soil hydraulic spatial variability. The proposed approach showed that, under the agro-climatic conditions typical for the Mediterranean region, SIMODIS may be a valuable tool in managing irrigation to increase water productivity.     

山区灌溉技术及应用研究

解决干旱、半干旱山地的农用灌溉用水问题，是帮助干旱山区农民脱贫致富的关键。采用YD型移动式高扬程灌溉及SYD型移动式滴灌技术，具有投资少、转移快捷方便、灌溉效率高及增产增效等优势，通过典型干旱山区的应用研究，该灌溉技术具有推广使用价值。     

Farmers’ incentives to save water with new irrigation systems and water taxation—A case study of Serbian potato production

Drip irrigation systems and irrigation strategies like deficit irrigation (DI) and partial root drying (PRD) are potential water saving irrigation systems and strategies. This paper analyses the Serbian farmer's economic incentive to use these water saving systems and strategies instead of the present sprinkler irrigation. The analysis is a partial budgeting analysis, based on irrigation application efficiency from the literature, standard figures for power requirements, pumping efficiency and friction losses for various sources of water and pressure requirements, yields and water use from recent Serbian field experiments, as well as prices and cost structures for potatoes collected in the Belgrade region. The analysis shows that changing the present system and strategy can save a significant amount of water (almost 50%). At the same time, however, irrigation costs are also significantly increased (more than doubled), and the total production costs are increased by 10% (deficit drip irrigation) and 23% (PRD). Increased taxes on water, investment subsidies, increased energy prices, and an increased yield or yield quality may provide incentives for farmers to change to new systems and strategies. The analysis indicates that a 0.80 to 1.97 € m⁻³ water tax is needed to make deficit drip irrigation and PRD profitable. The socioeconomic cost of providing water for irrigation and the alternative value of saved water are probably not that high. Thus, water taxation may not be a socioeconomic efficient means to improve the irrigation water productivity of Serbian potato production. Drip irrigation and PRD may, however, also increase the yield quality, and a 10-23% quality premium (price increase) is needed to make deficit drip irrigation and PRD profitable.     

Social power,water control and irrigation systems

The principal finding of the study is that social power positions held by Egyptian farmers sharings a common watercourse do not have significant influence in the farmer's ability to control irrigation water distribution. Other variables used to describe irrigation management; location on the water course and farmers' use of more than one source of water to irrigate; also do not yield any explanations as to why particular farmers have more control over their irrigation than others. Farmers who have more control are less likely to be affected by other farmers' actions, physical problems on delivery canals, breakdown in pumps, and government officials actions. While differences in irrigation control among farmers exist, no single cause is identified. Two explanations for the findings are (1) water control is sufficient for a large percentage of Egyptian farmers, and (2) adequately explaining irrigation behavior cannot be done with separate variables.Deceased     

Using drainage systems for supplementary irrigation

The use of drainage systems for supplementary irrigation is widespread in The Netherlands. One of the operating policies is to raise the surface water level during the growing season in order to reduce drainage (water conservation) or to create subsurface irrigation. This type of operation is based on practical experience, which can be far from optimal.To obtain better founded operational water management rules a total soil water/surface water model was built. In a case study the effects of using the drainage system in a dual-purpose manner on the arable crop production were simulated with the model. Also, the operational rules for managing this type of dual-purpose drainage systems were derived.The average annual simulated increase in crop transpiration due to water conservation and water supply for subsurface irrigation are 6.0 and 5.4 mm.y^–1, respectively. This is equivalent with 520 × 10³ and 460 × 10³ Dfl.y^–1 for the pilot region (2 Dfl 1 US $). The corresponding investments and operational costs are 600 × 10³ Dfl and 9 × 10³ Dfl.y^–1 for water conservation and 3200 × 10³ Dfl and 128 × 10³ Dfl.y^–1 for subsurface irrigation. Hence, water conservation is economically very profitable, whereas subsurface irrigation is less attractive.Comparing the management according to the model with current practice in a water-board during 1983 and 1986 learned that benefits can increase with some 50 and 500 Dfl per ha per year, respectively.     

Irrigation timeliness indicators and application in smallholder irrigation systems in Zimbabwe

Timing of supply of irrigation water is an important measure of water management performance. Yet despite this widely accepted importance of timeliness, few studies have attempted to quantify this performance indicator. This paper suggests a methodology for quantifying timeliness. The indices thus generated are used to compare the performance of some types of smallholder irrigation schemes in Zimbabwe. Results indicate that applying measures of timeliness helps to assess water management practices across scheme types.The methodology given in this paper differentiates between timely irrigation deliveries which meet Crop Water Requirements (CWR) and surplus water supplies due to poor timeliness which cannot be used by the crop, hence denoting wastage. The timeliness indices provide more information regarding management practices than simple measures of total water applications over a given season.     

Usefulness and limitations of decision support systems for improving irrigation scheme management

SIMIS (the FAO Scheme Irrigation Management Information System) is a decision support system that integrates tools and performance indicators to facilitate the planning and management of irrigation schemes. The authors used SIMIS to compute performance indicators in an irrigation scheme in Southern Spain that were used to identify distribution system constraints affecting the flexibility of water deliveries and to identify scheme sectors where deliveries could not meet the predicted crop water demands. Applying SIMIS, the authors and the irrigation scheme manager evaluated measures to overcome the constraints for future irrigation campaigns, and to refine the water orders made every 2 weeks to the basin authority. On the other hand, SIMIS presented limitations to the evaluation of on-demand delivery schedules. To overcome these limitations, an external model, developed outside SIMIS, showed that the current distribution network of the scheme has the capacity to deliver water on-demand only if a slight water deficit is accepted during the peak demand period. The analysis showed that by relaxing the stringency of the quality of operation of on-demand systems, rotation systems may be transformed into on-demand systems without changing their structures. This analysis could also be done using Clément's hypothesis, but doing so resulted in overestimates of the quality of operation and of the relative irrigation supply.     

Performance of agency-managed and farmer-managed irrigation systems: A comparative case study at Chitwan, Nepal

Management reforms are considered one of the best alternatives in increasing efficiency of the irrigation systems. Transfer of day-to-day operation and maintenance to farmers is not a new concept. However due to lags, even now it is a hot issue in developing countries and Nepal is not an exception. In this context of growing argument about the transfer of management of public irrigation systems to the Water Users' Group, this paper examines the comparative performance of farmer-managed and agency-managed irrigation systems. Khageri Irrigation System in the Chitwan district of Nepal was taken as the study site where complete management transfer has been done in 1996. The situations before and after complete transfer were compared. Intensive case studies of the selected farmers showed that equity in distribution of water and leakage had significantly improved after management transfer. Logit analysis revealed that age and education level of the household head, distance from main canal, leakage of the canal and equity in distribution are significantly related to the satisfaction level of the beneficiary farmers from FMIS compared to AMIS. However, landholding size of the respondent farmer has no significant effect. Similarly results from t-test revealed that rice productivity and overall profits from agriculture has also increased significantly due to irrigation management transfer.     

Regional partnerships to assist public-private investments in irrigation systems

Public-private partnerships have been implemented throughout the world since the 1970s with mixed results. This is mainly due to the lack of long run commitments from governments and other parties involved, lack of scientific understanding regarding clear short-term and long-term potential biophysical and socio-economic, policy and legal consequences, and lack of trust between the partners. We present a Regional Irrigation Business Partnership (RIBP) model, which is capable of efficiently utilising research output and government policies for sustainable public-private irrigation planning and investment. Unlike other public-private partnership models, the RIBP is based on robust assessment of biophysical, hydrologic, socio-economic, political and legal aspects of water management. The RIBP model provides a crucial link between research and infrastructure investments while minimising short-term and long-term risks. The business investment framework involves iterative feedback from research and policy for identifying markets, defining products and establishing a legislatively and institutionally acceptable route to market as part of the feasibility assessment process. The RIBP model is based on the principle that sharing risks, rewards, and responsibilities coupled with sufficient investment incentives will motivate actors in water management to invest in irrigation infrastructure that saves water and generates better outcomes for the environment. We describe application of the RIBP model in the Coleambally Irrigation Area in New South Wales, Australia.     

Management guidelines for efficient irrigation of vegetables using closed-end level furrows

Closed-end level furrows are commonly used to irrigate vegetables in the Lower Colorado River region (LCRR). The application efficiency of furrow irrigation in this area is often low. The objective of this study is to develop management tools and guidelines for the efficient irrigation of vegetables using closed-end level furrows. The study consisted of field experiment and modeling (model calibration, model verification, and the development of management tools by simulation). Field experiments were performed over a period of 27 months. Infiltration parameters were estimated for four soil textural groups (i.e., moderately coarse textured, medium textured, moderately fine textured, and fine textured soils) using a two-point method modified for closed-end level furrows. Model verification shows that the surface irrigation hydraulic model used in this study (SRFR) is capable of simulating the furrow irrigation process with acceptable levels of accuracy. Results of the study also indicate that adequate and efficient irrigations can be achieved using closed-end level furrows through the proper selection of unit inlet flow rate, Q_o, and cutoff time, t_co. However, given the soil and crop combinations in the LCRR, sometimes significant increases in irrigation efficiency, compared to present levels, can be attained only if furrow lengths are shorter than the typical size currently in use in the LCRR. Limitations of the proposed management tools and on-going research to address these limitations are briefly discussed.     

Prediction of surface irrigation advance using soil intake properties

A simple method for predicting surface irrigation advance trajectories using infiltration parameters and inflow rate as inputs was developed. The difference between the inflow rate and the sum of infiltration rates over the wetted portion of the field equals the flow rate available for advance. An average (characteristic) infiltration rate ahead of the wet portion is computed using a fixed time step. An advance step (for a fixed time step) is calculated from the ratio of the flow rate available for advance and characteristic infiltration rate. Predictions of advance by the proposed method were compared with field observations, with the kinematic wave model, and with analytical solutions of Philip and Farrell (1964). In all cases, the method provided predictions that were in good agreement with field observations, and performed similarly to the kinematic wave model. The method offers a simple and efficient tool for prediction and evaluation of surface irrigation systems under various soil types and variable inflow rates. The method is particularly useful for predictions in fields with spatially and temporally variable intake properties.