Journal of Irrigation and Drainage Engineering

Pivot weirs are used in irrigation networks to regulate water surface elevation and flow rate measurements. For ease of operation, this type of weir can be implemented in automatic operations of irrigation networks. However, little research has been performed to determine the head-discharge equation for this type of weir. In this research, two equations are used to calculate discharge over the pivot weir. The first equation is Kindsvater-Carter’s discharge equation, which is commonly used as the normal rectangular weir equation. The second is derived from energy and critical depth equations. To determine the coefficients of these equations, some tests were performed on an experimental model using three pivot weirs with different angles ($\theta =0$, 20, 40, 60, 80, and 90°) and side contractions of 0.4, 0.6, and 0.8. The experimental data were then compiled with the United States Bureau of Reclamation (USBR) data, and based on dimensional analysis, the discharge coefficients were estimated for free and submerged flow conditions. The accuracy of two equations under free-flow conditions was within $\pm 15$ and $\pm 10\%$, respectively. The range of error for the second equation in submerged flow condition was less than $\pm 20\%$, and the submergence factor was between 0.2 and 0.9, which is acceptable for application.

This work presents and applies a new methodology to find the optimal topography of a surface irrigation field, achieving a theoretically uniform surface irrigation. For any variant on surface irrigation (basin, border or furrow, with open or blocked end), the method’s result is a particular curved topographical shape of a field. This shape distributes water evenly over the field so that distribution uniformity is theoretically 100% and deep percolation disappears. The methodology was applied to two theoretical cases: (1) a one-dimensional blocked-end field, and (2) a two-dimensional square field with corner inflow. For each case, the methodology reached a particular topography in which distribution uniformity was near 100%. To put this methodology into practice, the optimized topography (which has a curved shape) can be fitted with two or more different slopes. An example is shown in which a real field was laser-levelled with two consecutive slopes to fit the optimized topography; it previously was calculated with the methodology presented in this paper. The irrigation was evaluated before and after the optimization. The results indicated an increase of distribution uniformity from 82 to 96%. The topographic optimization methodology offers new information about topography influence on irrigation performance indicators. The main practical conclusion is that this method can be useful to determine the best slope, set of slopes or curved shape when levelling any field for surface irrigation.

Sediment-laden runoff is the primary pollutant in many watersheds, so sediment basins are commonly used to remove sediment before it leaves the site. In fact, for construction sites such basins are often required by statute. Sediment basins are usually drained by perforated vertical risers and more recently by floating skimmers. Whereas a traditional riser discharges primarily from its lower orifices because of the higher heads that exist at greater depths, skimmers drain the cleaner water at the top of the water column, thereby increasing sediment retention. The authors have developed an alternative solid state skimmer (given the moniker “solid state” because it has no moving parts) that provides a similar skimming function, but also provides the additional benefits of varying flow rate with head and serving as its own principal spillway. The solid state skimmer is comprised of two concentric vertical risers. Columns of orifices cut into each riser act in series such that the flow into the outer riser is always dominated by flow through the uppermost wetted orifices, enabling skimming of water from a basin for the purpose of increasing sediment retention.

This paper analyzes long-term trends and sudden changes in hydro-climatic variables (i.e., runoff) in Iran’s Aidoghmoush basin during 1971–2000 using the nonparametric Mann-Kendall test and curves of cumulative runoff versus rainfall and cumulative runoff versus temperature The use of the Mann-Kendall test with a 99% confidence level revealed a decreasing trend in annual rainfall and total runoff and an increasing trend in temperature. A sudden change in the gradient of the cumulative curves in 1988 indicated that the relation between climatic variables and runoff is influenced by human activities (agricultural water use). The interval 1971–2000 was separated into a baseline interval (1971–1988) and an impact interval (1989–2000), during which human activities affected runoff. The five-parameter hydrologic model of IHACRES (Identification of unit Hydrographs and Component flows from Rainfall, Evaporation, and Streamflow data) was calibrated and verified over the baseline interval to determine the contribution of human activities and climatic variability to the change in runoff. Runoff was simulated with the hydrologic model for the interval 1989–2000, during which human activities reduced runoff. Results show that climate variability and human activities decreased the runoff in the Aidoghmoush river basin by 79 and 21%, respectively.

Estimating the return-flow fractions of different consumptive water uses for the effective management of water resource allocation and operation in a river basin is an essential issue. The purpose of this study was to estimate the return-flow fractions of domestic, industrial, and agricultural water demands, as well as to determine the contributed inflow from the return flows into surface and groundwater resources. This was done through the automatic calibration of a river basin software program, in conjunction with a genetic meta-search calibration algorithm. In this study, the calibration of parameters was made possible by using the customization features of the model. Calibration was done for three combinations of the objective functions. The results of the study demonstrated that the best and most logical results occurred in the third condition, which was a calibration by the objective function, including the root-mean-square error (RMSE) of the river basin’s outflow and the RMSE of the aquifer’s level. The fractions of the return flow from domestic, industrial, and agricultural demands in the case study of the Shian Basin in western Iran, were obtained as 87, 76, and 18%, respectively.

A biobjective programming model is developed with fuzzy inputs in response to the complexity of conflicting objectives and uncertainties in irrigation water allocation systems. The model is capable of increasing agricultural water productivity and meanwhile reducing irrigation water shortage, compromising the concerns of both agricultural decision makers and farmers. Moreover, the developed model adequately considers the fuzzy uncertainties in parameters, constraints, and objective functions. The potential of the developed model is shown by applying to a real case study in northwest China. Results show alternative decisions for irrigation water allocation under different flow levels, and indicate that the effectiveness of the trading program is explicitly affected by uncertainties expressed as fuzziness. Comparison with a commonly used model for irrigation water allocation demonstrates the feasibility and applicability of the developed model, which is helpful for the development of water-saving high-efficiency agriculture.

In an urban environment, vegetated roofs are sustainable systems that provide a variety of valuable benefits, such as the reduction of stormwater volumes and the mitigation of urban heat islands strongly linked to their evaporative processes. The evapotranspiration (ET) is one of the most important processes of the hydrological cycle, but it also represents one of the most difficult hydrological phenomena to quantify because of the complex interaction between the ground surface, vegetation, and atmosphere. However, an accurate computation of ET from vegetated roofs is essential to properly predict the benefits of such systems. The aim of this paper is to evaluate and compare three ET models for the prediction of ET from a green roof: a combination model and two temperature-based models under Mediterranean climate conditions. The study was carried out on an experimental green roof, located at University of Calabria, Italy, by using the onsite data with a time step of 5 min and a monitoring period ranging from September 2013 to June 2014. The study demonstrated that the two temperature-based models produced results that were in good agreement with those obtained from the combination model when onsite data from an extensive green roof located in a Mediterranean area were used.