Assessing Sprinkler Irrigation Performance Using Field Evaluations at the Medjerda Lower Valley of Tunisia

10 Pags., 6 Figs., 7 Tabls.Irrigation uniformity and wind drift and evaporation losses (WDEL) are major concerns for the design and management of sprinkler irrigation systems under arid or semi-arid conditions. Field trials were carried out to assess irrigation uniformity and WDEL under various wind velocities, sprinkler spacings and operating pressure heads. Based on experimental data, a frequency analysis was performed to infer the occurrence probability of a given uniformity coefficient (UC). In addition, statistical regressions were used to model WDEL as a function of different climatic variables. Increasing the operating pressure head improved uniformity at low wind speeds. It was shown that UC has been severely impaired at wind speeds above 4 m/s. In the prevailing wind conditions, the frequency analysis showed that a sprinkler spacing of 12 m × 12 m provided the best uniformity. In the local conditions, it is recommended to stop irrigation when wind velocity exceeds 4 m/s. Moreover, it was shown that wind speed and relative humidity were the main significant variables influencing WDEL.The authors are thankful to the INRGREF for the valuable support of this research.Peer reviewe

A case study for irrigation modernisation: II: Scenario analysis

42 Pags.- 5 Tabls.- 9 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774Surface irrigation simulation models have seldom been used in engineering practise, and district modernisation is not an exception. Surface irrigation evaluations were performed in the Almudévar irrigation district to obtain the parameters required for surface irrigation modelling. The total district irrigated area was divided into 92 design units, for which a characteristic blocked-end border was defined. Simulation was used to establish the current irrigation performance in each design unit, and district performance contour maps were built. Irrigation performance was characterised using potential application efficiency, with an average of 54%, and irrigation time, averaging 6 h ha−1. Simulated potential application efficiency of the low quarter was similar to the seasonal irrigation performance index (an estimate of irrigation efficiency) presented in the companion paper. A set of seven modernisation scenarios was defined. Two strategies were identified to improve the potential application efficiency in the scenarios: increase the irrigation discharge into the current blocked-end borders and/or substitute the current system with a solid set sprinkler irrigation system. The performance of each scenario was estimated using irrigation models to determine efficiency, water conservation and irrigation time. The modernisation investment costs were estimated and compared to the performance of each scenario. The best results (potential application efficiency of 77%, reduced water allocation by 14.4 106 m3 year−1) were obtained by a combination of blocked-end irrigation with a discharge of 200 l s−1 and sprinkler irrigation in the areas where surface irrigation efficiency could not attain 50%. The investment cost for this scenario was 3932 Euro ha−1. More expensive scenarios did not guarantee better performance.This work was sponsored in part by the INIA (Institute of Agricultural Research of the Government of Spain). The Mediterranean Agronomic Institute of Zaragoza (IAMZ–CIHEAM) awarded a scholarship to A. Slatni that made this research possible.Peer reviewe

Assessing alternate furrow strategies for potato at the Cherfech irrigation district of Tunisia

39 Paf., 4 Tabl., 5 Fig. The definitive version is available at: http://www.sciencedirect.com/science/journal/15375110Irrigated agriculture faces intense competition for water in Mediterranean environments. In this paper, alternate furrow irrigation (AFI) was explored for a potato crop in the conditions of the Cherfech irrigation district, located in the Medjerda project of northern Tunisia. A field experiment was performed involving seven furrow irrigations in three irrigation treatments: alternate furrow irrigation, fixed furrow irrigation (FFI), and conventional furrow irrigation (CFI). Crop yield and water productivity were determined in all treatments. The experiment involved detailed irrigation evaluation and soil water measurements in the first three irrigation events. Soil infiltration (estimated with a surface irrigation model) was larger for CFI than for AFI or FFI. This finding was confirmed by the average irrigation depths, which amounted to 65, 60 and 91 mm for the AFI, FFI and CFI treatments, respectively. Application and irrigation efficiency were higher in FFI than in AFI, while in CFI efficiency was much lower. Water productivity (expressed as the ratio of yield to irrigation water) amounted to 8.0, 8.7 and 5.9 kg m−3 for the AFI, FFI and CFI treatments, respectively. Soil water-yield simulations indicated that alternate furrow irrigation did not result in reduced yield, neither for the experimental treatment nor for deficit irrigation scenarios characterised by six or five irrigation events. Alternate furrow irrigation stands as a simple management technique resulting in relevant water conservation in the local conditions.This research was partially funded by INRGREF (Tunisia), and by the Agencia Española de Cooperación y Desarrollo (AECID) of the Government of Spain, through grant A/7661/07.Peer reviewe

Day and night time sprinkler irrigated tomato: Irrigation performance and crop yield

31 Pag., 5 Tabl., 7 Fig.The effect of day time vs. night time sprinkler irrigation on irrigation performance and tomato crop yield is assessed in this paper for the conditions of Tunisia. Field experiments were performed at the experimental station of Cherfech under two rectangular sprinkler spacings: 24 × 18 m and 18 × 18 m, denoted as plots M1 and M2, respectively. Results of performance evaluations indicate a significant effect of climatic and operation conditions on irrigation uniformity and wind drift and evaporation losses (WDEL). Experimental data were used to calibrate and validate a ballistic solid-set sprinkler irrigation simulation model and a soil-water-yield crop model. Based on the analysis of the main meteorological parameters during the irrigation season, the validated models were used to simulate night time irrigation (characterised by moderate wind speed and evaporative demand). Simulation results indicate that night time irrigation would greatly improve performance in comparison to day time operation: WDEL decreased from 24 to 7%, while irrigation uniformity increased from 50 to 64% in M1 and from 71 to 80% in M2. Simulated results showed that night time irrigation decreased relative yield losses (from 26 to 16% in M1 and from 11 to 3% in M2), as well as improving the spatial variability of crop yield (simulated yield CV in M2 decreased from 17 to 6%). Adoption of night irrigation in the study area will finally depend on local socioeconomic and water management constraints.This research was partially funded by INRGREF (Tunisia), and by the Agencia Española de Cooperación y Desarrollo (AECID) of the Government of Spain, through grant A/7661/07.Peer reviewe

A case study for irrigation modernisation: I. Characterisation of the district and analysis of water delivery records

40 Pags.- 2 Tabls.- 11 Figs. The definitive version is available at: http://www.sciencedirect.com/science/journal/03783774The analysis of water management in irrigated districts is highly relevant. The present work highlights the principal irrigation management problems of the irrigation district of Almudévar, a representative surface irrigation district located in the northeast of Spain. The predominant irrigation system is blocked-end borders. The study included three phases: (1) assessment of crop water requirements of the main crops of the study area; (2) characterisation of soil depth and soil water retention; and (3) analysis of the current irrigation practices based on the study of the 1994 water records of the district. The following irrigation management problems were identified: (1) the mean volume of water billed to the farmers was 43% higher than the net irrigation requirements; (2) the volume of water billed to the farmers were inversely related to the farm size; (3) few, widely spaced, large irrigation events; (4) large delay time in water delivery; and (5) in selected crops and/or areas, water billing was lower than the net irrigation requirements, indicating the presence of marginal areas or heavily subsidised crops. This research could be applied in other areas of traditional surface irrigation systems. The goal of this methodology is to diagnose the actual level of water management and to provide data for the modernisation of the irrigation district. In a companion paper, a decision support system for the modernisation of the district is presented.This work was sponsored in part by the INIA (Institute of Agricultural Research of the Government of Spain). The Mediterranean Agronomic Institute of Zaragoza (IAMZ-CIHEAM) awarded scholarships to A. Bensaci and A. Slatni that made this research possible.Peer reviewe

Improvement of durum wheat (Triticum durum) surface irrigation in swelling soils

7 Pags., 2 Figs., 7 Tabls.This study is targeted to improve surface irrigation performance of durum wheat in swelling soils. For this purpose, furrow and border irrigation trials were carried out and evaluated under different soil water depletion rates, furrow spacing and unitary inlet discharges. Irrigation was triggered whenever the soil water depletion rate reached a predetermined threshold. A comprehensive irrigation evaluation produced hydraulic, agronomic and economic indicators, such as application efficiency, distribution uniformity, crop yield, gross margin and water productivity. Experimental results showed that supplied water depths exceeded soil water deficits, inducing relevant vertical and lateral water losses. Although border and furrow irrigation crop yields were virtually tantamount (about 5.5 Mg/ha), furrow irrigation was the system of choice. An irrigation strategy based on a furrow spacing of 150 cm, an inlet discharge of 2 l/s/furrow and a soil water depletion rate of 30% required a gross water depth of 4300 m3/ha/yr and generated an optimum crop yield of 58 qx/ha. In the analyzed range of soil water depletion, the gross margin and water value amounted to 1064 - 1390 Tunisian Dinar per hectare (TD/ha) and 0.39 - 0.44 TD/m3, respectively, for a furrow spacing of 150 cm.The authors are thankful to the INRGREF for the valuable support of this research.Peer reviewe

Evaluation des paramètres d’infiltration en irrigation à la raie sur trois types de sol

16 Pags.- 4 Tabls.- 7 Figs.[AR] يهدف هذا العمل إلى تحليل ثلاثة طرق لتحديد ترشيح الماء لثلاثة أنواع من التربة بشمال وبوسط البلاد (Elliot et Walker, التونسية. تعتمد هذه الطرق المستعملة على علاقات تجريبية وهي: طريقة النقطتين .(Philip et Farrell, وطريقة فليب و فرار ( 1964 (Shepard, 1982 ، طريقة النقطة الواحدة ( 1993 ) من أجل هذا قمنا بمتابعة سيلان الماء في خطوط الري على ثلاثة أنواع من التربة التي تحتوي على مخزون مائي يساوي 100 بالنسبة للأول و 120 للثاني والثالثة 145 مم/م. كما وقع قيس منسوب الماء في خطوط الري وكمية الماء في التربة قبل وبعد الري. هذه القياسات وقع استغلالها لتحديد معادلة ترشيح الماء بالنسبة للمقاربات المستعملة في هذه الدراسة. بالنسبة لمجموع أنواع التربة، بينت نتائج الدراسة أن طريقة النقطتين هي الطريقة المثلى للحصول على أحسن مقاربة لتحديد ترشيح الماء في التربة (Elliot et Walker, 1982) (Philip et في المقابل أظهرت النتائج أن طريقة فليب و فرار .(Kostiakov, وذلك باستعمال معادلة ( 1932 هي الأسواء من حيث مقاربة تحديد ترشيح الماء. (Philip, التي تعتمد على معادلة ( 1957 Farrell, 1964)[FR] L’objectif de la présente étude est l’analyse de trois méthodes de détermination de la loi d’infiltration de l’eau dans le sol pour trois types de sol des régions du Nord et du Centre de la Tunisie. Les trois méthodes utilisées sont basées sur des équations empiriques à savoir: méthode de deux points (Elliot et Walker, 1982), méthode d’un point (Shepard, 1993) et la méthode de Philip et Farrell (1964). Pour ce faire, le suivi de l’avancement de l’eau a été réalisé sur trois types de sol dont la réserve utile est de 100, 120 et 145 mm/m. Ces mesures ont été utilisées afin de prédire les constantes de l’équation d’infiltration par les trois méthodes étudiées. Pour les trois sites d’étude, les résultats de simulation et l’analyse statistique ont montré que la méthode de deux points permet d’obtenir le meilleur ajustement des courbes d’infiltration et ce en utilisant les constantes de Kostiakov (1932) alors que les résultats exhibant les plus faibles niveaux d’ajustement sont obtenus en utilisant les constantes de l’équation de Philip (1957) déterminées par la méthode de Philip et Farrell (1964).[EN] The objective of this study is to analyze three methods of determining the infiltration rate for three types of soils located in the North and Center of Tunisia. For this purpose, three empirical infiltration method were used: the one –point method (Shepard, 1993), two-point method (Elliot et Walker, 1982) and Philip and Farrell method (1964). Measurements of the advance of water were performed in the three soils with holding capacity of 100, 120 and 145 mm/m in order to predict the infiltration constants. Results of the advance of the water front and statistical analysis indicates that using the constants of Kostiakov (1932), the two-point method shows the best feet of the cumulative infiltration curves. Likewise, results exhibiting the lowest fitting levels are obtained using Philip equation (1957) constants determined by Farrell and Philip method.Peer reviewe