灌漑・排水システム工学

Use low-quality water has become part of Egypt water strategies to meet its demands especially in the agricultural sector. This study investigates the irrigation water (mixed freshwater with agricultural drainage water), drainage water, soil drainage, salinity and groundwater for Gelbana region (2500 hectare new reclaimed area since 2000) at the East South El-Qantara, North Sinai, Egypt. The findings indicated that irrigation water quality was slightly saline. The drainage water and groundwater were medium saline. Soil was a poorly medium dense sand, have an electrical conductivity (EC) varying from 1 to 4 dS/m, and the vertical drainage was low efficiency. for sustainable cultivation it is recommended that (1) applying subsurface drainage system to improve washing of soil salts (2) changing the cropping system at the scheme to meet soil salinity levels (3) periodic monitoring for the irrigation water, drainage water, soil salinity, and the groundwater are important issue to manage crop pattern and drainage water.

A three year field study was conducted in Origamali area at Abga ragial Administrative unit, Belil Locality, South Darfur State Nyala City, during the rainy season in 2013, 2014 and 2015. The aim of this study was to test the effect of four intra-row spacing treatments (50 cm, 75 cm, 100cm and 125 cm) on cowpea performance. A completely randomized design (CRD) with four replications was used to identify differences between treatments. It was found that closer intra-row spacing had significant effect on plant density and plant height while it had no significant effect on survival rate, pod yield or seed yield. It is therefore suggested that, for seed and pod production under rainfall conditions in South Darfur, wider spacing may be a rational strategy for farmers as it does not lower pod and seed yield which is advantageous when intercropping is practiced. Further studies are needed to clarify the effect of wider spacing on pod and grain yield in farming systems that adopt intercropping.

Theoretical analysis of slope effects on the spatial patterns of the pressure head profiles of an irrigation lateral is presented in the companion paper. Results of the analysis are evaluated here based on simulations. Simulations were conducted for data sets covering a wide range of lateral parameters. The results show that the pressure profile patterns of a lateral, and possibly the locations of the pressure extrema along the lateral, can be determined by comparing the negative lateral slope with the friction slope at the inlet and/or distal ends, confirming an important inference of the analysis. The simulation study also shows that the full range of variation of lateral pressure profile patterns can be differentiated into the three distinct categories defined based on theory. While results of the analysis developed in the companion paper are generally true, they nonetheless produce only particular solutions (i.e., solutions specific to a given lateral slope). The simulation results, however, provide additional insights, into the relationships between slopes and pressure profile patterns, which would enhance the practical significance of the theoretical analysis. For each data set, considered, simulation outputs reveal that there exists a unique pair of threshold slopes that delimits the feasible range of variation of the lateral slope into three subintervals, each with a specific lateral pressure head profile pattern. Furthermore, the spatial pattern of the simulated lateral pressure profiles, within each of these slope subintervals, corresponds to one of the three categories defined in the companion paper. Hence, the full range of variation of the lateral pressure profile patterns can be completely characterized based on a pair of threshold slopes that are unique to the lateral, which is an advantage. Results of the simulation study are, nonetheless, empirical. Thus, more comprehensive studies are needed to conclusively establish the broader significance of these results.

The pressure head profile of an irrigation lateral is a function of the hydraulic and geometric characteristics of the lateral and its slope. Slope effects on pressure variability along a lateral are typically limited. However, for a lateral with a spatially invariant parameter set well-defined relationships can be discerned between lateral slopes and the spatial patterns of the lateral pressure profiles. Thus, a comprehensive understanding of these relationships can be useful in the evaluation of lateral hydraulic simulation models and design recommendations. Existing studies have examined slope effects on the locations of pressure head extreme, along a lateral, in the context of hydraulic design of laterals. This paper presents a comprehensive analysis of slope effects on lateral pressure head profile patterns. The monotonic properties, with respect to distance from inlet, of lateral slope and friction slope profiles coupled with the pressure slope equation are used here to determine the full range of variation of lateral pressure head profile patterns as a function of lateral slope. Overall, the analysis show that the pressure profile patterns of a lateral, and possibly the locations of the pressure extreme along the lateral, can be determined by comparing the negative of the lateral slope with the corresponding friction slope at the upstream and/or downstream ends of the profile. The results also show that the full range of variation of the pressure profile patterns of a lateral, as affected by slope, consists of three distinct categories. These include a profile pattern that is increasing or decreasing, with distance from the inlet, over the entire length of the lateral and one that combines both trends within the length of the lateral. The relationships between lateral slopes and pressure profile patterns, deduced here through theoretical analysis, will be evaluated in a companion paper based on simulations.

Open canals are the common method used to convey water for irrigation in Ethiopian sugar estate, however, little or no attention is given to the evaluation of conveyance systems. Consequently, many of the existing conveyance systems are deteriorating in their physical structures, operation and management. Due to this the current study was conducted to quantify the amount of seepage loss through lined and unlined irrigation canals of Tendaho sugar estate. Seepage losses were determined by inflow-out flow method for primary, secondary, and tertiary canals, while water velocity was determined using a current-meter. The average seepage losses were resulted in 0.55% per 100 m (0.0126 lit/s/m²) and 0.84% per 100 m (0.0180 lit/s/m²) for lined and unlined primary canals whereas, 3.65% per 100 m (0.0391 lit/s/m²) and 4.27% per 100 m (0.0248 lit/s/m²) were obtained for secondary and tertiary canals, respectively. In the result, primary canal seepage loss was higher in unlined than in lined by 0.0054 lit/s/m² of wetted area of the canal. The result reveals that high seepage loss for both lined and unlined canals may be attributed through damage of geomembrane lining and poor maintenance of earthen canals. To minimize excess seepage and improve the conveyance system, overall maintenance and repair of canals should be done in the Estate.  

Field assessment to evaluate the performance of small-scale irrigation projects plays a vital role in improving the existing projects and assist engineers in designing new systems so that irrigation practice becomes sustainable. This study was initiated to investigate the causes of under-performance of the Wesha small-scale irrigation project. The performance indicators that were used to evaluate the irrigation project are technical that directly or indirectly affect water deliveries and water spreading effects. Seven technical performance indices used; namely, conveyance efficiency, application efficiency, water storage efficiency, water distribution uniformity, deep percolation fraction, runoff ratio and sustainability. The evaluation was done using nine irrigation events on three representative farmers’ fields (selected from the head, middle and tail of the command area). During each irrigation event, water inflow and tail water outflow measurements; determination of soil moisture before and after each irrigation event; interviewing of irrigators; field observations and collection of secondary data were made. The results show that performance of the irrigation project is unsatisfactory in terms of conveyance efficiency, application efficiency, deep percolation fraction and sustainability with mean values of 65.39%, 46.78%, 48.43% and 30%, respectively. This shows that large volume of water is lost as steady-state and transient losses from canals and from irrigated fields. However, the distribution uniformity, water storage efficiency and runoff ratio are satisfactory with mean values of 88.3%, 97.63% and 4.45%, respectively indicating high deep-percolation loss. During the study period, on-site soil erosion, temporary water logging and illegal canal breaching are the observed major problems associated with the farmers’ irrigation practices. Weak operation and maintenance of the project is also witnessed and thus its sustainability is uncertain. 

The paper provides a comparative analysis of Technical efficiencies of two household irrigation technologies; rope and washer and pulley practiced by farmers in two pilot areas of rural communities in Amhara region of Ethiopia. The paper attempted to identify factors that contribute to the inefficiencies in using these technologies for the production of irrigated crops. Stochastic Frontier Analysis (SFA) was used for estimating the efficiency levels and the ordinal regression analysis has been employed to factor out determinants of inefficiency. Experimental data has been used from two selected communities in two different districts of the Amhara region. The results obtained from the stochastic frontier analysis indicate that farmers are operating at a significantly lower efficiency level of average 70% indicating the existence of a room for increased production without additional investment. A number of socioeconomic, demographic and farm characteristics were identified as factors contributing to the inefficiency which can be used as a policy tool to boost production to the best possible.

Several developed inland valleys for rice production were abandoned due to poor design or implementation. The Bankandi Inland Valley (BIV) is a contour bunds system developed in 2006 by a development project, currently experiencing a systematic waterlogging.
This study assessed:
i. The waterlogging vs. changing hydro-climatic conditions relationship;
ii. The hydrological design and implementation of water control infrastructures; and
iii. How digital elevation models (DEMs) data could be used for inland valleys development.
To investigate the waterlogging vs. changing hydro-climatic conditions (precipitation and discharge), the conceptual HBV model was applied; coupled with break and trend detections tests. To evaluate the accuracy of the location of drainage flume and contour bunds, a topographic survey using a D-GPS was performed. To explore free DEMs as support tool in the development of inland valley, the Shuttle Radar Topography Mission 1 and the Advanced Spaceborne Thermal Emission and Reflection Radiometer 1, were used.
The results show that:
i. the waterlogging was not related to changing environmental conditions;
ii. major flaws including bunds not implemented on contour lines contribute to the waterlogging;
iii. free DEMs were not accurate enough for valley development.
The overall diagnostic of BIV entails conducting basic hydrological investigations prior to implementation.

Building on existing technology that utilizes capacitance sensors and low-cost microcontrollers, we designed, assembled and tested a self-contained irrigation system for controlling substrate volumetric moisture content in container-grown ornamental plants. In the prototype system described here, compatible software is embedded within the microcontroller, real-time measurements appear on a liquid-crystal display screen, and data are stored on a secure digital card, thereby allowing irrigation threshold settings to be changed without the need for reprogramming the microcontroller. The system components are readily available and affordably priced, making the unit a useful management option for improving irrigation scheduling for growers that do not wish to invest in more costly wireless network systems. In evaluation trials using 5-week-old containerized zinnia seedlings, the automated system reliably controlled irrigation thresholds ranging from 0.155 to 0.425 m³ m^-3. During the trial period each threshold was maintained for 5-7 days during which time substrate VMC varied ± 0.04 to ±0.06 m3 m-3, and the volume of water required to sustain each threshold (as calculated from data collected and stored on the system secure digital card) was within 3% of the actual quantity of water collected in plastic containers attached to the same irrigation line.

Modeling provides important planning tools that can be used in management of land and water resources which can be used in the understanding of dynamic processes and prediction of the existing processes. The evolution of a wide range of hydrologic catchment models employing the physical based and data driven approach introduces the need for objective test benchmark to assess the merits of different models in reconciling alternative approaches. The main objective of this study was to model stream flow and sediment yield by using ANN and SWAT models for the Upper Main Beles gauged catchment. The two models were calibrated and validated at Main Beles gauging station for both stream flow and sediment yield yielding reasonable results in monthly and daily time step. Two days antecedent values were considered during formulation of possible inputs for daily basis and no antecedent value were considered for monthly time step modeling for ANN model. Modeling by SWAT for stream flow yields a mean monthly stream flow of 65.28 m3 /s showing 2.48% deviation whereas the MLP neural model prediction was 67.37 m3 /s showing 5.76% deviation from the observed mean monthly flow. Total mean annual Sediment yield loading from Upper Main Beles simulated by SWAT and ANN model was 4.81 and 5.97 ton/ha/year underestimated by 12.9% and overestimated by 8.1% respectively excluding bed load contribution. The total mean annual sediment yield that was drawn from Upper Main Beles predicted by SWAT and ANN model was found 1,602,845.92 ton and 1,989,395.05 ton respectively. Sediment yield modeling by MLP neural model in both daily and monthly time step predicts better than SWAT including daily stream flow modeling. The calibrated parameter values of the two models can be considered for further hydrologic simulation of the watershed and their application in consideration of their simplicity in data requirement, purpose, prediction accuracy and change in land use dynamics of the watershed.

n order to interpret the surface water quality of drinking water sources of Tongyu River and Mangshe River in Yancheng city, China, 18 water quality parameters were selected and data from 9 sampling sites during 2010 to 2015 from were collected and analyzed by multivariate statistical techniques, including cluster analysis (CA), principal component analysis (PCA), and factor analysis (FA). The sampling sites were classified into three clusters based on their similarities using a hierarchical CA, which represented relative low pollution sites, moderate pollution sites, and relative high pollution sites. By PCA/FA, six latent factors were identified that accounted for 75.39% of the total variance, representing the influences of organic pollution, fecal pollution, biochemical reactions, nutrients, domestic sewage, and natural factors, respectively. By pollution source analysis, the results were obtained that Sites 1, 2, and 3 were almost completely unaffected by various pollution sources, Sites 4 and 5 were polluted with industrial and domestic discharge, Sites 6, 7, and 8 were polluted with point and nonpoint sources from industrial activity, agriculture, and domestic drainage, and Site 9 was severely polluted with untreated domestic discharge from nearby inhabitants. The results verified that multivariate statistical techniques are useful, and may be necessary for analyzing and interpreting large, complex surface water quality databases, which could help managers optimize action plans to control drinking water quality.