Journal of Irrigation and Drainage Engineering

It has long been recognized that reliable, robust, and automated instrumentation for the measurement of soil moisture content can be extremely useful, if not essential, in hydrological, environmental, and agricultural applications. A number of automated techniques for point measurement of soil water content have been developed to operational level over the past few decades. While each of those techniques has been individually calibrated by the gravimetric method, typically under laboratory conditions, there have been few studies that made a direct comparison between the various techniques, particularly under field conditions. This paper compares ${\text{ECH}}_2\text{O}$ probes, EC-5 (both sensors based on capacitance measurements, developed by Decagon Devices) and time domain reflectometer sensors (CS616 Campbell Scientific Water Content Reflectometer), with gravimetric data and with each other, under field conditions. Data were collected during two field experiments characterized by different soils and a wide range of soil moistures, resulting from irrigation/drying cycle. Results show that all the tested probes give acceptable results after being calibrated in the field. The capacitive sensors can be used in each type of soil with the same calibration equation, independently from depth, with root mean square error (RMSE) ranging between 2.5 and 3.6%. Time Domain Reflectometry probes showed a dependence on depth but a lower RMSE (1.6%).

The interbasin water transfer project is an alternative to balance the nonuniform temporal and spatial distribution of water resources and water demands, especially in arid and semi arid regions. A water transfer project can be executed if it is environmentally and economically justified. In this study, the feasibility of two interbasin water transfer projects from Karoon River in the western part of Iran to the central part of the country is investigated. An optimization model with an economic objective function to maximize the net benefit of the interbasin water transfer projects is developed. The planning horizon of the model is 23 years (the length of historical data); and it is solved using genetic algorithm. In order to consider environmental impacts of water transfer projects, a water quality simulation model has been used. Then, an Artificial Neural Network model is trained based on the simulation results of a river water quality model in order to be coupled with the optimization model. The outputs of the optimization model are the value of economic gain of the sending (Karoon) basin to offset the loss of agricultural income and environmental costs. The optimal polices for water transfer during the planning horizon has been generated using the coupled simulation-optimization model. Then, operating rules are developed using a K Nearest Neighborhood model for the real time water transfer operation. The results show the significant value of using the proposed algorithm and economic evaluation for water transfer projects.

One of the problems in irrigation structures is sedimentation control in the inlet to the irrigation networks. Water quality for agriculture requires that the sediments be controlled at their entrance point to the networks. This is possible by constructing a settling basin (SB). The bigger the basins, the better the retardation of the sediments but the expenses are higher too. Different mathematical models are developed for SBs. Most of these models show the relationship between efficiency and effective parameters with mathematical formulas. In this research, a computer simulation model was written for calculating the efficiency of a SB. Using this model, another computer program was developed in which design parameters (length, width, depth, slope, and water velocity in the basin) were determined such that the basin has the specified characteristics and minimum construction costs. In this respect, operations research and a lexicographic enumeration algorithm was used. Validation of the computer simulation was performed by applying it to two SBs in Nekouabad diversion dam, west of Isfahan, Iran. The average actual efficiencies of right and left Nekouabad SBs were 31.2 and 36.2%, respectively, while the average calculated efficiencies for right and left SBs were 35.4 and 40.2%, respectively. Application of this program for designing an optimum SB for Nekouabad diversion dam was shown to be promising.

To withdraw large quantities of groundwater from the alluvial aquifers for various uses near riverbeds, radial collector (RC) wells are often preferable to the installation of several small diameter tube wells. In regions where rivers are not perennial or have low flow conditions during most part of the year, the RC wells are placed in the riverbed to obtain uninterrupted supply of naturally filtered groundwater through highly permeable saturated riverbed aquifers. Due to the complexities of flow, no exact analytical solution exists to provide steady state discharge drawdown relationship for RC well. Numerical model construction using finite difference or finite element method is quite cumbersome because of the radial orientation of laterals. To overcome these difficulties, in this study a steady state simulation model based on analytic element method (AEM) is developed to simulate the discharge-drawdown relation for RC well in an unconfined riverbed aquifer. In the model, line-sink elements are used to represent stream as well as radial laterals with specified conductance. The model is used to study the effects of different lateral configurations, hydraulic conductivity of riverbed aquifer, radius of influence and conductance of laterals on the well discharge, and consequent drawdown. Further based on the results of simulations using the AEM model, an approximate empirical equation is developed to obtain the discharge of RC well readily for design purpose. Further, the developed model has been applied to a field study and results are obtained for different plausible configurations of radial wells. The proposed methodology based on the application of AEM modeling tool, has been found to be efficient in constructing riverbed aquifer model with RC well. The proposed model is recommended in designing new collector well by providing minimum length of laterals for the sustained yield.

Scour control downstream of hydraulic structures is an important topic in hydraulic engineering. Block ramps or rock chutes are often used to control scour downstream of hydraulic structures and have the peculiarity to be ecofriendly. Although these structures assure great energy dissipation, the rapid passage from supercritical to subcritical flow at the toe results in a scour hole with geometric parameters that have to be evaluated in order to avoid foundation problems. For this reason, the analysis of the scour process and the comprehension of the hydrodynamic mechanisms on which it is based are extremely important. In this paper, the results of systematic experimental tests are shown that analyze both the influence of the stilling basin tailwater depth and the ramp toe stabilizing structures, for both uniform and nonuniform channel bed materials. In fact, block ramps are generally stabilized by inserting piles or micropiles at the toe. The upper edge level of piles or micropiles was found a relevant parameter for the scour hole geometry. Simple novel relationships that account for tailwater depth, pile position, and bed material gradation are developed to evaluate the main lengths of the scour hole, in the case in which a free hydraulic jump in a mobile bed occurs. These simple relationships give engineers helpful instruments in block ramp design.

The main objective of this research is to compare different irrigation methods based upon a parametric evaluation system in an area of 29,300 ha in the Abbas plain located in the Elam Province, in the west of Iran. The soil properties of the study area such as texture, depth, electrical conductivity, drainage, calcium carbonate content, and slope were derived from a semidetailed soil study carried out on the Abbas Plain on a scale of 1:20,000. Once the soil properties were analyzed and evaluated, suitability maps were generated for surface, sprinkle, and drip irrigation methods using remote sensing techniques and geographic information system. The obtained results showed that for 16,125 ha (55.03%) of the study area surface irrigation method was highly recommended; whereas for 16,600 ha (56.66%) of the study area a sprinkle irrigation method would provide to be extremely efficient and suitable; moreover, it was found that 15,425 ha (52.65%) of the study area was highly suitable for drip irrigation methods; however, one soil series coded 9 and covering an area of 2,150 ha (7.34%) was incompatible for sprinkle and surface irrigation systems. For drip irrigation systems the unsuitable lands did not exist in this zone. The results demonstrated that by applying sprinkle irrigation instead of surface and drip irrigation methods, the arability of 21,250 ha (72.53%) in the Abbas Plain will improve. In addition by applying drip irrigation instead of surface and sprinkle irrigation methods, the land suitability of 6,275 ha (21.42%) of this plain will improve. The comparison of the different types of irrigation techniques revealed that the sprinkle and drip irrigation methods were more effective and efficient than the surface irrigation methods for improving land productivity. It is of note, however, that the main limiting factor in using either surface and/or sprinkle irrigation methods in this area is soil texture and the main limiting factor in using drip irrigation methods were soil calcium carbonate content and soil texture.

Accurate estimation of reference evapotranspiration $\left({\text{ET}}_0\right)$ is essential for irrigation practice. Conversion from pan evaporation data to reference evapotranspiration is commonly practiced. The objective of this study was to evaluate the reliability of simplified pan-based approaches for estimating ${\text{ET}}_0$ directly that do not require the data of relative humidity and wind speed. In this study, three pan-based (FAO-24 pan, Snyder ${\text{ET}}_0$ , and Ghare ${\text{ET}}_0$ ) equations were compared against lysimeter measurements of grass evapotranspiration using daily data from Policoro, Italy. Based on summary statistics, the Snyder ${\text{ET}}_0$ equation ranked first with the lowest RMSE value $\left(0.449\text{mm}{\text{day}}^{-1}\right)$ . The pan-based equations were additional tested using mean daily data collected in Novi Sad, Serbia. The Snyder ${\text{ET}}_0$ equation best matched ${\text{ET}}_0$ estimates by Penman-Monteith equation at Novi Sad with lowest root mean square error value of $0.288\text{mm}{\text{day}}^{-1}$ . The obtained results demonstrate that simplified pan-based equations can be successful alternative to FAO-56 Penman-Monteith equation for estimating reference evapotranspiration. The overall results recommended Snyder ${\text{ET}}_0$ equation for pan evaporation to evapotranspiration conversions. The Snyder ${\text{ET}}_0$ equation consistently provides better results compared to FAO-24 pan equation, although required measurements of only one weather parameter pan evaporation.

The high design standards for the preservation of the urban water environment result in more detention basins in residential areas. The steep channel and outfall pipe from a detention basin can be hazardous to children and small animals. During an event, a trapped person may flow with water toward the outfall entrance. When the outfall pipe is gradually blocked, the flow force acting on the blocking body can be pinning at the beginning to eventually deadly. It is not clear as to how to quantify the pinning force on the block during the closure of flow because the number of unknown forces is greater than the number of equations for force balance. This paper presents a new approach using the method of superposition to calculate the pinning force with and without a blockage at the culvert entrance. The analysis conducted in this paper verifies that the pinning force on the clogging block is dominated by the flow dynamic force until the flow becomes discontinued. As soon as the hydrostatic force is developed, the pinning force can be lethal. This study confirms that an outfall pipe shall be protected by a trash rack with its surface area 4 times the culvert opening area. As long as the continuity of flow is sustained by the blocked rack, the hydrostatic force will not be developed or a chance for survival remains.

This study brings to the attention the difficulty imposed by the design on the development of a self cleansing storm sewer based on a general rule of minimum water velocity of 0.75 m/s under pipe full capacity and suggests the Camp’s criterion as an alternative. The key finding is the determination of the lower limit of flow strengths above which the Camp’s criterion can be applied to warrant the development of a more efficient storm sewer system. The lower limit is adjusted for storm sewers with loose or rigid boundary serving two transport conditions: to sustain equal sediment mobility on pipe invert instead of selective transport, and to avoid progressive deposition of finer grains due to low and reducing water flows.

Simple method and explicit equations are proposed for estimating the parameters of leaky aquifers from drawdown at an observation well, which avoid the curve matching or initial estimate of the parameter. The proposed method is computationally simple and the calculations can be performed even on a handheld calculator. The application of the methods is illustrated, using published data sets. The new method yields quick and accurate estimates of the leaky-aquifer parameters, if observed drawdowns do not contain large errors. The proposed method can also analyze the early drawdowns for accurate characteristics/parameters of a confined aquifer, if the conductance of the aquitard is assigned a zero value. It is hoped that the proposed method would be of help to field engineers and practitioners.