Cumulative relative water supply: A methodology for assessing irrigation system performance

This paper discusses the usefulness and limitations of using the concept of Relative Water Supply (RWS) for evaluating the performance of irrigation systems, with special reference to systems irrigating rice. It then describes and demonstrates the use of a modification of RWS called Cumulative Relative Water Supply (CRWS), which can be used in conjunction with RWS. The advantage of CRWS is that it provides a measure of the cumulated RWS throughout a season, both in absolute terms at any given time, and in terms of the overall seasonal trend. It allows comparison of performance of an irrigation system or subsystem both to the target, and to other systems or subsystems. It can therefore be used both as an analytical tool by researchers, and as an operational tool by managers. The use of CRWS in conjunction with RWS is illustrated with examples from Sri Lanka.     

Using satellite remote sensing to assess irrigation performance in Water User Associations in the Lower Gediz Basin, Turkey

The aim of this research was to assess the irrigation performance of the Salihli Right Bank, Salihli Left Bank, Ahmetli, Gokkaya, Turgutlu, Mesir, Sarikiz, Gediz, Menemen Right Bank and Menemen Left Bank Water User Associations (WUAs) in the Lower Gediz Basin in western Turkey, using remote sensing techniques. To reach this aim the performance of the irrigation system for the 2004 irrigation season was determined according to five indicators, namely overall consumed ratio (e_p), relative water supply (RWS), depleted fraction (DF), crop water deficit (CWD) and relative evapotranspiration (RET). Potential and actual evapotranspiration parameters used in determining these indicators were estimated according to the Surface Energy Balance Algorithm for Land (SEBAL) method using NOAA-16 satellite images.Seasonal averages of these indicators ranged from 0.59 to 2.26 for e_p, 0.47-1.66 for RWS, 0.43-1.31 for DF, 180.5-269.5 mm month⁻¹ for CWD, and 0.61-0.74 for RET. According to the seasonal average values of all the performance indicators, the irrigation performance of all WUAs was usually poor. The performance indicators showed that less irrigation water was supplied to WUAs than was needed. It was concluded that proximity to the source could be an advantage in obtaining water, and that when water was insufficient, groundwater in the crop root area could be used.     

Economic feasibility of growing capsicum crop under drip irrigation in West Bengal, India

Drip irrigation system has been one of the technical means to improve water use efficiency. In India, this system is gaining popularity among fruit growers and in water scarced area but a substantial area is being covered annually under vegetables crops. One of the major concerns raised by farmers about this system is its economic viability. In present study, the economic viability of drip irrigation system for growing capsicum crop based on discounted cash flow technique (Net present worth and Benefit cost ratio) was explored. Eight irrigation treatments were laid under drip with and without plastic mulch. The irrigation levels were taken as 1, 0.8 and 0.6 of the crop evapotranspiration. The pan evaporation method was used for estimation of reference evapotranspiration and Water Balance Approach was used for irrigation scheduling. The average amount of water supplied under treatment VD (100% irrigation requirement supplied with drip) was found to be 415 mm for whole growing season of the crop. Similarly the amount of water was found to be 332 mm and 249 mm for the treatment 0.8VD (80% irrigation requirement supplied with drip) and 0.6VD (60% irrigation requirement supplied with drip) respectively. Highest yield was recorded in case of treatment VD + PM (100% irrigation requirement supplied with drip plus plastic mulch) followed by VD. Yield under treatments 0.8VD, 0.6VD, 0.8VD + PM and 0.6VD + PM were significant while treatments VD, VF and VF + PM were at par with the treatment VD + PM. Net Present Worth (NPW) was found to be positive for all the treatments. The highest NPW was obtained under treatment VD as Rs. 309,734.90 and lowest was in case of 0.6VD + PM as Rs. 144,172.24. The yield per mm of water used was reported to be at higher side as 35 in both the treatments VD and VD + PM. But the yield per mm of water used was found to be lowest as 18.07 and 19 in case of VF and VF + PM respectively.     

Assessing basin irrigation and scheduling strategies for saving irrigation water and controlling salinity in the upper Yellow River Basin, China

Water saving in irrigation is a key concern in the Yellow River basin. Excessive water diversions for irrigation waste water and produce waterlogging problems during the crop season and soil salinization in low lands. Supply control and inadequate functionality of the drainage system were identified as main factors for poor water management at farm level. Their improvement condition the adoption of water saving and salinity control practices. Focusing on the farm scale, studies to assess the potential for water savings included: (a) field evaluation of current basin irrigation practices and further use of the simulation models SRFR and SIRMOD to generate alternative improvements for the surface irrigation systems and (b) the use of the ISAREG model to simulate the present and improved irrigation scheduling alternatives taking into consideration salinity control. Models were used interactively to define alternatives for the irrigation systems and scheduling that would minimize percolation and produce water savings. Foreseen improvements refer to basin inflow discharges, land leveling and irrigation scheduling that could result in water savings of 33% relative to actual demand. These improvements would also reduce percolation and maintain water table depths below 1 m thereby reducing soil salinization.     

Experiences of farmer participation in irrigation management: Mula command Maharashtra State,India

A major storage dam on the Mula River in Maharashtra was constructed in the early 1970s to irrigate about 80 000 ha in 149 drought prone villages. Even though the project is operational since 1977–78 and the storage supplies were as per design, in subsequent years the irrigated area has not exceeded 40 000 ha even in the best rainfall and storage years. Among the complexity of factors responsible for this gross under utillisation, the water allocation and distribution procedures are the important ones. The conventional method of allocation and distribution and its weaknesses are described. In 1981–82, the Rotational Water Supply System (RWS) was introduced on a pilot basis in a few minors to improve the water use efficiency. A review of the experience shows that even though the adoption of RWS has improved the situation, especially on the technical side, little headway has been effected on the organisation of farmers. The micro-level distribution system is still managed by the bureaucracy. As such the RWS has reached a performance plateau. Further gains are possible, only if the groups are encouraged to take over the management and the needed policy changes for graduating the RWS into a farmer managed system are introduced. Among these changes, the important are the assurance of the financial viability of the groups, choice of profitable crops and extension work to impart stability to the groups.     

Corn crop response under managing different irrigation and salinity levels

Non-uniformity of water distribution under irrigation system creates both deficit and surplus irrigation areas. Water salinity can be hazard on crop production; however, there is little information on the interaction of irrigation and salinity conditions on corn (Zea Mays) growth and production. This study evaluated the effect of salinity and irrigation levels on growth and yield of corn grown in the arid area of Egypt. A field experiment was conducted using corn grown in northern Egypt at Quesina, Menofia in 2009 summer season to evaluate amount of water applied, salinity hazard and their interactions. Three salinity levels and five irrigation treatments were arranged in a randomized split-plot design with salinity treatments as main plots and irrigation rates within salinity treatments. Salinity treatments were to apply fresh water (0.89 dS m⁻¹), saline water (4.73 dS m⁻¹), or mixing fresh plus saline water (2.81 dS m⁻¹). Irrigation treatments were a ratio of crop evapotranspiration (ET) as: 0.6ET, 0.8ET, 1.0ET, 1.2ET, and 1.4ET. In well-watered conditions (1.0ET), seasonal water usable by corn was 453, 423, and 380 mm for 0.89EC, 2.81EC and 4.73EC over the 122-day growing season, respectively. Soil salt accumulation was significantly increased by either irrigation salinity increase or amount decrease. But, soil infiltration was significantly decreased by either salinity level or its interaction with irrigation amount. Leaf temperature, transpiration rate, and stomata resistance were significantly affected by both irrigation and salinity levels with interaction. Leaf area index, harvest index, and yield were the greatest when fresh and adequate irrigation was applied. Grain yield was significantly affected in a linear relationship (r² ≥ 0.95) by either irrigation or salinity conditions with no interaction. An optimal irrigation scheduling was statistically developed based on crop response for a given salinity level to extrapolate data from the small experiment (uniform condition) to big field (non-uniformity condition) under the experiment constraints.     

Use of simulation models to evaluate irrigation performance including water productivity, risk and system analyses

 Worsening water scarcity will increase pressure to use water more productively. In the classical view of irrigation research, some important aspects are often ignored: the total water balance approach, productivity of water, food security, and irrigation-system level analyses. These four approaches were evaluated using a detailed agro-hydrological model applied to an irrigation system in western Turkey. Emphasis was placed on the two dominant crops in the area: cotton and grapes. According to the classical point of view, the only result would be to irrigate the cotton with 1000 mm and the grapes with 800 mm. From the water productivity point of view, however, the water productivity of grapes appeared to be maximal without any irrigation; while for the cotton, irrigation at 600 mm maximizes water productivity. To minimize risks and increase yield stability, grapes perform better than cotton. Finally, from the irrigation system point of view, decisions can be made about the desirable cropping pattern and the distribution of water between crops. With limited amounts of water available for irrigation, a cropping pattern consisting mainly of grapes is desired; while with higher water availability, a mixture of cotton and grapes is preferable. The methods presented provide a clear methodology with which to achieve the most productive use of water. Received: 3 June 1999     

Yield and economic return of vegetable crops under variable irrigation

 Field experiments were conducted for 2 years (1997 and 1998) on sandy loam soil in northwestern Botswana to study the effect of five levels of pan evaporation replenishment (20, 40, 60, 80 and 100%) on marketable yield, yield components, irrigation production efficiency and economic return of winter broccoli, carrot, rape and cabbage under a drip irrigation method. The highest mean marketable yield (2 years) of broccoli (19.1 t/ha), carrot (58.9 and 32.9 t/ha), rape (61.8 t/ha) and cabbage (97.2 t/ha) was recorded at 80% of pan evaporation replenishment. The irrigation production efficiency of broccoli (5.9 kg/m³), rape (14.6 kg/m³) and cabbage (23.6 kg/m³) was maximum at 80, 20 and 60% of pan evaporation replenishment respectively. Irrigation replenishment up to 80% of pan evaporation loss did not influence the irrigation production efficiency for total and root yield of carrot. The results revealed that a further increase in irrigation amount resulting from 100% of pan evaporation replenishment did not increase the marketable yield of crops but reduced the irrigation production efficiency significantly. The seasonal water applied and marketable yield of broccoli, carrot, rape and cabbage showed quadratic relationships (R ² = 0.85–0.98), which can be used for allocating irrigation water within and between the crops. The net return increased with the increase in pan evaporation replenishment. The results revealed that the rape crop is the most remunerative, followed by cabbage, broccoli and carrot. Received: 2 November 1998     

Management trends and responses to water scarcity in an irrigation scheme of Southern Spain

Improvement of irrigation management in areas subjected to periods of water scarcity requires good knowledge of system performance over long time periods. We have conducted a study aimed at characterizing the behaviour of an irrigated area encompassing over 7000 ha in Southern Spain, since its inception in 1991. Detailed cropping pattern and plot water use records allowed the assessment of irrigation scheme performance using a simulation model that computed maximum irrigation requirements for every plot during the first 15 years of system operations. The ratio of irrigation water used to maximum irrigation requirements (Annual Relative Irrigation Supply, ARIS) was well below 1 and oscillated around 0.6 in the 12 years that there were no water supply restrictions in the district. The ARIS values varied among crops, however, from values between 0.2 and 0.3 for sunflower and wheat, to values approaching 1 for cotton and sugar beet. Farmer interviews revealed some of the causes for the low irrigation water usage which were mainly associated with the attempt to balance profitability and stability, and with the lack of incentives to achieve maximum yields in crops subsidized by the Common Agricultural Policy (CAP) of the European Union. The response to water scarcity was also documented through interviews and demonstrated that the change in crop choice is the primary reaction to an anticipated constraint in water supply. Water productivity (value of production divided by the volume of irrigation water delivered; WP) in the district was moderate and highly variable (around 2€ m⁻³) and did not increase with time. Irrigation water productivity (increase in production value due to irrigation divided by irrigation water delivered) was much lower (0.65€ m⁻³) and also, it did not increase with time. The lack of improvement in WP, the low irrigation water usage, and the changes in cropping patterns over the first 15 years of operation indicate that performance trends in irrigated agriculture are determined by a complex mix of technical, economic, and socio-cultural factors, as those that characterized the behaviour of the Genil-Cabra irrigation scheme.     

Olive tree response to irrigation with wastewater from the table olive industry

A field experiment was conducted to examine the effect of drip irrigation using wastewater from a table olive industry on physiological, nutritional and yield parameters of olive trees (Olea europaea L.). Very limited information, if any, exists, on the potential of recycling this kind of wastewater in agriculture. Two types of wastewater were used in the experiment, the first with SAR and EC values of 12–56 and 3.5–4.2 dS m⁻¹, respectively, and the second 73–90 and 4.3–6.0 dS m⁻¹. In general, this kind of wastewater has a highly variable composition and SAR values that are too high for agricultural purposes. Olive trees rapidly responded to wastewater application. Compared to the control (fresh water), the more saline wastewater caused important decreases in leaf water potential, stomatal conductance to H₂O and the photosynthesis rate after only 15 days of irrigation, the reduction being more pronounced after 2 months of irrigation. This treatment also caused a rapid, significant reduction in leaf N concentration, as compared with the N level in the trees before irrigation. Both types of wastewater significantly reduced olive yield, compared to that obtained in the control. These results indicate that this kind of wastewater is unsuitable for application to olive orchards under irrigation. Received: 16 August 1999     

Influence of cross-regulator settings on the offtake discharge in a modern irrigation network

The hydraulic performance of canals and related delivery structures is highly dependent on the management of cross-regulators. The HEC-RAS model was applied to Ordibehesht Canal at the Doroodzan irrigation network, northwest of Fars province in Iran for evaluation of water delivery performance due to operation of cross-regulators. Discharge deviations of offtakes due to cross-regulator gate position changes and deviations of water delivery equity were evaluated. Results showed that small changes in gate positions of check structures (cross-regulators) cause considerable changes in the offtake discharges and equity (spatial uniformity) of water delivery to the offtakes along the main canal. Results of the study led to the development of two sensitivity indicators. “Offtake sensitivity to check setting” that represents the changes in offtake discharges due to changes in cross-regulator setting, and “Sensitivity of the equity indicator to the gate position change” are the two developed indicators which can be used for better management of water delivery systems.     

Irrigation scheduling and irrigation systems: optimising irrigation efficiency for container ornamental shrubs

Water use and plant growth and quality were compared across different nursery stock beds, different methods of applying irrigation, and different methods of scheduling irrigation. With overhead irrigation, scheduling of irrigation according to plant demand, along with an irrigation system designed to maximise irrigation uniformity, resulted in substantial water savings, without reducing plant quality. This was the case in both wet and dry years. In the dry year, plant quality was particularly good when grown on a sub-irrigated sand bed; this system also used less water than any of the overhead irrigation systems. Two different systems were effective in scheduling overhead irrigation, one based on the volumetric moisture in the growing substrate, and the other based on plant evapotranspiration. The latter was determined with a small sensor with wet and dry artificial “leaves”, the output of which correlated with that obtained following the Penman–Monteith method based on a full set of meteorological data.     

Evaluation of capacitance probes for optimal irrigation of citrus through soil moisture monitoring in an entisol profile

 Continuous monitoring of soil moisture content within and below the rooting zone can facilitate optimal irrigation scheduling aimed at minimizing both the effects of water stress on the plants, and also the leaching of water below the root zone, which can have adverse environmental effects. The use of Sentek capacitance probes (EnviroSCAN RT5) in scheduling citrus irrigation was evaluated using 3-year-old Hamlin orange trees [Citrus sinensis (L.) Osb.] on Swingle citrumelo rootstock [Citrus paradisi Macf. × Poncirus trifoliata (L.) Raf.] grown in a Candler fine sand (hyperthermic, uncoated, Typic Quartzipsamments). Available soil moisture calculated according to capacitance probe readings of soil moisture agreed well with that calculated using soil water release curves determined in the laboratory. A utility program was developed to process the data collected by the capacitance probe into a spreadsheet format. Processed data were used to calculate soil water storage within and below the citrus root zone at desired time intervals. Irrigation set points (i.e., full point equivalent to maximum desirable water storage and refill points I and II) were defined based on field capacity determined both in the field and in the laboratory and permanent wilting point. It was possible to maintain the water content in the root zone between the full and refill points I and II during most of the growing season. Although soil water content in the root zone exceeded the full point during periods of high irrigation, it drained rapidly within 24–48 h after the end of such irrigation events. Using soil moisture depletion in the root zone during periods of low water application to estimate citrus evapotranspiration (ET), the calculated daily average ET during 10-day period in November was 1.33 mm day⁻¹. Received: 11 August 1998     

The influence of bearing cycles on olive oil production response to irrigation

Water requirements for olive oil production and the effects of deficit irrigation were determined while considering the relative fruit loads on trees occurring as a result of biennial bearing cycles. Two Israeli olive (Olea europaea) varieties (Barnea and Souri) were evaluated for growth and yield parameters in a 4-year field study where five relative irrigation rates were applied. Increasing irrigation increased stem water potential, vegetative growth, and olive fruit yield with the increases tapering off at application rates reaching 75–100% of potential crop evapotranspiration. Tree water status, growth, and fruit characteristic parameters were highly affected by both fruit load and by irrigation level. Oil yield increases as a function of increased irrigation were initiated for each cultivar only following an ‘off’ season when the treatments lead to higher vegetative growth. The increased oil yields as a function of increased irrigation were primarily explained by higher tree-scale capacity for carrying fruit, especially as irrigation alleviated measureable water stress. For the Barnea cultivar in ‘on’ years, a secondary effect due to increased oil per fruit as irrigation increased was evident, particularly at the higher application rates.     

Hyperspectral reflectance data processing through cluster and principal component analysis for estimating irrigation and yield related indicators

Management of agricultural practices such as irrigation by using remotely sensed data requires background data obtained from field experiments carried out under controlled conditions. In this study, spectral and agronomic data from field trials consisting of six different irrigation treatments were used to derive new spectral indicators for estimating growth level and water use status of dwarf green beans. Spectral reflectance (Ref) values were smoothed and first-order derivative spectra (ρ) were calculated. Linear regression and multivariate analysis (cluster and principal component analysis) were done between agronomic indicators and both the smoothed spectral reflectance (R) and ρ of each individual wavelength between 650 and 1100 nm. Based on those calculations, the most appropriate wavelengths were selected for each agronomic indicator and new combinations were calculated by using rationing, differencing, normalized differencing and multiple regression. The ratio between ρ measured at 950 or 960 nm and 1020 nm wavelengths provided estimates in an error band of 2.47 bar for Leaf Water Potential (LWP) and 3.18% for Leaf Water Content (LWC). An equation based on ρ740 and ρ980 was developed to estimate Leaf Relative Water Content (LRWC). In the same manner, the ρ at 820 and 970 nm provided a good estimate of crop water use and the ρ values at 770 and 960 nm were critical for the calculation of Leaf Area Index (LAI) and dry biomass. It was also determined that the ratio of R930 to R670 can be applied to yield estimation.     

Loquat as a crop model for successful deficit irrigation

During three consecutive seasons, two different deficit irrigation strategies were compared with control fully irrigated trees regarding their capacity to induce early bloom and harvest in “Algerie” loquat. The first strategy, a continuous deficit irrigation strategy, consisted in a uniform reduction of 20% water needs through the entire season; the second strategy, a regulated deficit irrigation approach, while accounting for the same global reduction of 20% loquat water needs, concentrated water shortages after harvest from mid-May through the end of August. Regulated deficit irrigation resulted more successful. Postharvest regulated deficit irrigation advanced full bloom 10–20 days depending on the season. Such enhancement led to more precocious and valuable yield, with an average increase of fruit value of 0.21 € kg⁻¹. The effects of continuous deficit irrigation were less noticeable and average fruit value was increased 0.08 € kg⁻¹. Yield and fruit quality were not affected for the different deficit irrigation strategies. Water savings established around 1450 m³ ha⁻¹ year⁻¹. Deficit irrigation rose water use efficiency up to more than a 40%.     

A modified checkbook irrigation method based on GIS-coupled model for regional irrigation scheduling

In this study, a regional irrigation schedule optimization method was proposed and applied in Fengqiu County in the North China Plain, which often suffers serious soil water drainage and nitrogen (N) leaching problems caused by excessive irrigation. The irrigation scheduling method was established by integrating the ‘checkbook irrigation method’ into a GIS-coupled soil water and nitrogen management model (WNMM) as an extension. The soil water and crop information required by the checkbook method, and previously collected from field observations, was estimated by the WNMM. By replacing manually observed data with simulated data from WNMM, the application range of the checkbook method could be extended from field scale to regional scale. The WNMM and the checkbook irrigation method were both validated by field experiments in the study region. The irrigation experiment in fluvo–aquic soil showed that the checkbook method had excellent performance; soil water drainage and N leaching were reduced by 83.1 and 85.6%, respectively, when compared with local farmers’ flood irrigation. Using the validated WNMM, the performance of checkbook irrigation in an entire winter wheat and summer maize rotation was also validated: the average soil water drainage and N leaching in four types of soils decreased from 331 to 75 mm year⁻¹ and 47.7 to 9.3 kg ha⁻¹ year⁻¹, respectively; and average irrigation water use efficiency increased from 26.5 to 57.2 kg ha⁻¹ mm⁻¹. The regional irrigation schedule optimization method based on WNMM was applied in Fengqiu County. The results showed a good effect on saving irrigation water, decreasing soil water drainage and then saving agricultural inputs. In a typical meteorological year, it could save >110 mm of irrigation water on average, translating to >7.26 × 10⁷ m³ of agricultural water saved each year within the county. Annual soil water drainage was reduced to <143 mm and N leaching to <27 kg ha⁻¹ in most soils, all of which were significantly lower than local farmers’ flood irrigation. In the mean time, crop yield also had an average increase of 2,890 kg ha⁻¹ when checkbook irrigation was applied.     

Assessment of water delivery efficiency in irrigation canals using performance indicators

Agricultural water is delivered by open irrigation canals in system of reservoirs with a widespread distribution in South Korea. Traditional irrigation management problems include water distribution systems with less capacity than the peak demand, irregular delivery rates, and low irrigation efficiency and uniformity. It is necessary to strategically compare the estimated irrigation demands with the actual water supplies for decision making in order to maintain the water supply according to the demand. Accurate measurement and monitoring of water distribution systems is essential in order to solve the problems of water efficiency and availability. Auto water level gauges installed at the head and tail sections of each irrigation canal in the Dongjin River were used to measure the discharge during irrigation periods. In this study, we introduced an approach to assess the water delivery performance indicators of the open irrigation canals, which is essential for identifying the key issues for water management improvement. The irrigation efficiencies according to the water delivery performance indicators were measured with an automatic water gauge in the irrigation canals and were calculated from the spatial and temporal distribution of the water supply for the lack of planning in water delivery. The calculated performance indicators are useful to understand the irrigator behavior and general irrigation trends. Analysis of the results yielded insights into possible improvement methods in order to develop water management policies that enable irrigation planners to improve the temporal uniformity and equity in the water distribution.     

Soil water distribution, uniformity and water-use efficiency under alternate furrow irrigation in arid areas

Soil water distribution, irrigation water advance and uniformity, yield production and water-use efficiency (WUE) were tested with a new irrigation method for irrigated maize in an arid area with seasonal rainfall of 77.5–88.0 mm for 2 years (1997 and 1998). Irrigation was applied through furrows in three ways: alternate furrow irrigation (AFI), fixed furrow irrigation (FFI) and conventional furrow irrigation (CFI). AFI means that one of the two neighboring furrows was alternately irrigated during consecutive watering. FFI means that irrigation was fixed to one of the two neighboring furrows. CFI was the conventional method where every furrow was irrigated during each watering. Each irrigation method was further divided into three treatments using different irrigation amounts: i.e. 45, 30, and 22.5 mm water for each watering. Results showed that the soil water contents in the two neighboring furrows of AFI remained different until the next irrigation with a higher water content in the previously irrigated furrow. Infiltration in CFI was deeper than that in AFI and FFI. The time of water advance did not differ between AFI, FFI and CFI at all distances monitored, and water advanced at a similar rate in all the treatments. The Christiansen uniformity coefficient of water content in the soil (CU_s) was used to evaluate the uniformity of irrigated water distribution and showed no decrease in AFI and FFI, although irrigation water use was smaller than in CFI. Root development was significantly enhanced by AFI treatment. Primary root numbers, total root dry weight and root density were all higher in AFI than in the FFI and CFI treatments. Less irrigation significantly reduced the total root dry weight and plant height in both the FFI and CFI treatments but this was less substantial with AFI treatments. The most surprising result was that AFI maintained high grain yield with up to a 50% reduction in irrigation amount, while the FFI and CFI treatments all showed a substantial decrease of yield with reduced irrigation. As a result, WUE for irrigated water was substantially increased. We conclude that AFI is an effective water-saving irrigation method in arid areas where maize production relies heavily on repeated irrigation. Received: 16 October 1999     

Performance assessment of small irrigation schemes along the Mauritanian banks of the Senegal River

Irrigation plays a fundamental role in world food provision but, to date, it has performed below expectations in Sub-Saharan Africa. The present study assesses and diagnoses the performance of 22 small and medium size community-managed irrigation schemes, mainly devoted to rice production, in different locations along the Mauritanian banks of the Lower Senegal River. The evaluations followed the Rapid Appraisal Process in which semi-structured interviews were held with representatives of the Cooperatives’ Boards in charge of each scheme to obtain information about the organisation of the cooperative, land tenure, irrigation system and organization, cropping pattern and soils. Additionally, for each irrigation scheme, the water-delivery service was characterized by making qualitative and comparative observations during field inspections; the pumping station's performance was diagnosed by a local specialist; the discharge at the head of the system was measured; daily irrigation time was recorded; and crop yields were determined by plot sampling. Then a set of performance indicators was computed. Water delivery capacity referred to irrigated areas was insufficient in a third of the schemes, and this insufficiency was exacerbated by poor maintenance. Irrigation intensity in habilitated areas was rather low being less than 0.66 in 50% of the schemes. The average productivity of land, irrigation water, and fuel (3.38 t ha⁻¹, 0.30 kg m⁻³ and 2.37 kg kWh⁻¹, respectively) were well below potential.