Journal of Irrigation and Drainage Engineering

This paper develops and evaluates rule curves of reservoir operation and compares them for baseline and future periods. The rules are calculated by genetic programming (GP). Also, the rules extracted are based on the rate of inflow, storage volume, and downstream irrigation network demand. The objective function used is the minimization of the average of squared monthly relative deficiencies in the allocation of water to irrigation demand. The study focuses on the reservoir system as well as the downstream irrigation network of Aidoghmoush dam in East Azerbaijan, Iran, under baseline conditions (time interval 1987–2000) and climate change conditions (time interval 2026–2039). To investigate the optimal allocation policy, three operational scenarios are considered: (1) development of current rules under baseline conditions; (2) employment of current rules for future conditions; and (3) development of future rules for future conditions. Results show that the current allocation policy (resulting from current optimal rules) should be modified under climatic change conditions. Also, the investigation indicates that the application of a future optimal allocation policy under future conditions relative to current rules under current conditions decreases (improves) the root-mean-square error (RMSE) and mean absolute error (MAE) performance criteria approximately 29 and 30%, respectively. In addition, efficiency indicators in the optimal allocation of reservoir water are calculated under climate change (policy used in the third operational scenario) and compared with its corresponding values in baseline conditions. Results show that under climate change conditions as compared to the baseline period, indexes of reliability, vulnerability, and resiliency, respectively, decrease 50%, increase 6%, and decrease 14%. Awareness of this issue by planners and decision makers can propel them to reduce the volume of network water requirements. This may be realized through changes, e.g., in the cropping pattern and cultivation area.

Two novel generalized analytical solutions of nondimensional specific energy and specific force equations for flow in rectangular open channels are obtained, which enable direct and explicit calculation of the alternate and sequent depths for the given nondimensional specific energy and specific force, respectively. Hydrostatic pressure and uniform velocity distributions across flow depth have been assumed, and friction loss in the flow has been neglected, while deriving the new solutions. Each generalized solution yields only three particular solutions out of which only two solutions giving positive values for the depth of flow are of practical significance. The particular solutions/equations of practical significance pertain to the alternate depths and sequent depths in the cases of nondimensional specific energy and specific force, respectively, and are distinguishable for subcritical and supercritical flow. The new solutions are compact (handy), computationally simple, and useful to the field of engineers and practitioners in directly solving the problems of transitions in width and elevation of the channel bottom, hydraulic jump, and length of the stilling basins. Hopefully, these solutions will possibly end the persistent search for a long time for handy generalized analytical solutions of the specific energy and specific force equations in a rectangular open channel.

Irrigation is the most common and standard practice for maintaining turfgrass and landscape plants in residential settings. The main objective of this study was to quantify the residential irrigation water use in Cary, North Carolina. A subobjective was to develop distributions of monthly reference evapotranspiration (${\mathrm{ET}}_o$) and gross irrigation requirements (GIRs) for the area using long-term weather data. As part of the subobjective, an investigation was performed to compare daily measured solar radiation with two empirical methods of estimating solar radiation ($R_s$). The goal of this investigation was to determine the relative accuracy of these methods and to evaluate the impact of using $R_s$ estimates in the computation of ${\mathrm{ET}}_o$ and GIR for the Raleigh-Durham area, where Cary is located. Irrigation water use data from 2005 to 2007 for 120 randomly sampled residences were evaluated. The average lawn area of the sampled residences was $713{\mathrm{m}}^2$. None of the sampled households used drip irrigation. A negative correlation existed between the irrigated area and applied water depth. The May-October period accounted for 84–89% of the total annual outdoor water use for the 3 years evaluated. A trend of applying more water than the gross irrigation requirement was observed during the lawn renovation period (mid-September through late October). Solar radiation was computed using two methods: the Hargreaves and Samani method based on difference in maximum and minimum temperature, and the Doorenbos and Pruitt method based on percent possible sunshine. Solar radiation estimated using the percent possible sunshine method showed a strong relationship ($R^2=0.88$) with measured solar radiation and proved to be a much more reliable way of estimating solar radiation than the temperature difference method for the Raleigh-Durham region. Estimates of mean, median, and $P_{80}$ (80th percentile) monthly ${\mathrm{ET}}_o$ and GIR constructed from a 60-year data set show that ${\mathrm{ET}}_o$ tends to peak in July at an average of 154 mm, whereas GIR peaks in June with an average of 105 mm. The distribution of GIR is substantially more variable than ${\mathrm{ET}}_o$ due mostly to variability in rainfall, illustrating the difficulty in applying the correct amount of water consistently from year to year in subhumid to humid regions.

A study was conducted in Cary, North Carolina, in the spring and summer of 2009 with the purpose of evaluating the effectiveness of two “smart irrigation” controllers based on the amount of irrigation applied and resulting turf quality in residential settings. Twenty-four residential sites were selected, in clusters of four, representing six geographical areas within the town. Each geographical cluster included one site of each treatment. The treatments were standard irrigation controller with an add-on soil moisture sensor system (SMS); standard irrigation controller with an add-on evapotranspiration-based adjustment system (ET); standard irrigation controller using seasonal runtimes based on historical climate data (ED); and a control group which used a standard irrigation controller with no intervention (CON). Weekly water usage was obtained from irrigation meter readings and turf quality was characterized using a visual rating and a normalized difference vegetation index (NDVI) meter. Maximum water savings were achieved by the SMS treatment (42% less than CON), followed by ET and ED treatments. No statistical difference in average weekly water use was found between the ET group and the ED group provided with controller run-time guidance. The mean weekly visual turf quality index was highest for the SMS treatment, but only statistically different from the ED group. Average weekly NDVI was greatest for the ED group, although average NDVI values were not statistically different among any of the groups. Although water use was less during the 2009 study period contrasted against the three previous years for those receiving some form of intervention (ED, ET, and SMS), the same trend in water use was found by the CON group, rendering any findings in change in behavior inconclusive. Variability in water application by cooperator groups receiving an intervention decreased in the study period compared to the three previous years, suggesting an impact.

Physicochemical properties of a Haplic Chernozem soil were measured while applying fertigation in a natural grassland during the growing season in a hemiboreal climate with irrigation management based on the decision support system–fertigation simulator (DSS-FS) model. The experimental field was divided into four parcels which were exposed to four different irrigation treatments: fertigation with nutritive solution A [electrical conductivity $(\mathrm{EC})=2\mathrm{mS}·{\mathrm{cm}}^{-1}$, $\mathrm{pH}=6$), fertigation with nutritive solution B ($\mathrm{EC}=1\mathrm{mS}·{\mathrm{cm}}^{-1}$, $\mathrm{pH}=6$), irrigation with raw water without any injected fertilizers ($\mathrm{EC}=0.27\mathrm{mS}·{\mathrm{cm}}^{-1}$, $\mathrm{pH}=6.5$), and control parcel (no treatment). Rainfall effect on soil desalinization through salt leaching was monitored by comparing the evolution of soil electrical conductivity during and after the growing season. The soil electrical conductivity of the chemigated parcels (parcels A and B) was higher than the control parcels (parcels C and D) at the end of the growing season. This difference decreased significantly, becoming negligible after the winter due to an efficient desalinization effect of rain and snow.

Permeable pavement systems have been increasingly used for onsite storm water management. In this paper, an analytical equation is derived for calculating the long-term average storm water capture efficiency of permeable pavement systems. This analytical equation is obtained by using the derived probability distribution theory on the basis of the probabilistic models of rainfall event characteristics and the mathematical representations of the hydrologic processes occurring in permeable pavement systems. Simplifying assumptions are made in establishing these mathematical representations. The validity of these assumptions and the accuracy of the analytical equation are demonstrated by comparing the analytical equation results with those determined from a series of continuous simulations where no similar simplifying assumptions are made.

A numerical two-dimensional finite-volume model is developed to predict the moisture-based form of the Richard’s equation that describes the transient flow of water through homogeneous and heterogeneous unsaturated porous media from a trickle irrigation source in a cylindrical flow region. Clay loam soil is selected to represent the homogeneous porous media. This cylindrical flow domain of clay loam soil is initially at uniform volumetric water content. Numerical runs were conducted with a clay loam soil at water application rates from the trickle irrigation source at a small circular pond area. An assessment of the fully implicit and explicit time schemes and arithmetic and geometric mean weighing formulas are evaluated. A good agreement is obtained when comparing the experimental measured positions of the wetting front advance with the predicted results. In general, for numerical modeling of the unsaturated flow equation, the fully implicit time scheme with geometric mean weighing formula for estimating the approximate value of the nonlinear soil water diffusivity and hydraulic conductivity at the interface between adjacent control volumes can be recommended when the theta-based form of the Richard’s equation is solved. The predicted results show that the finite-volume method is mass conservative, and it is a recommended method for solving Richard’s equation.