Journal of Irrigation and Drainage Engineering

Net radiation is an important and site-specific component to determine reference evapotranspiration $\left({\mathrm{ET}}_0\right)$ . The empirical Angstrom coefficients for radiation estimation in the FAO56 Penman–Monteith (PM) equation were calibrated using observed daily solar radiation and actual sunshine duration on the Tibetan Plateau. The calibrated Angstom coefficients included annual coefficients for nine meteorological stations separately and aggregation of nine stations. The calibrated annual coefficients for each station separately were applied to estimate net radiation and further employed to estimate ${\mathrm{ET}}_0$ using the PM and the Priestley–Taylor (PT) equations on the Tibetan Plateau. Moreover, the Hargreaves (Harg) equation that requires only air temperature was also applied to estimate ${\mathrm{ET}}_0$ . Comparisons of three methods were conducted and the results showed that the PT method overestimated daily ${\mathrm{ET}}_0$ with respect to $\mathrm{PM}–{\mathrm{ET}}_0$ and the Harg method underestimated it at all meteorological stations. The PT method was more suitable for the study area in the absence of the parameters necessary for the calculation of $\mathrm{PM}–{\mathrm{ET}}_0$ . The Harg equation provides ${\mathrm{ET}}_0$ estimates when only air temperature is available and local calibration in the study can be applied on the Tibetan Plateau.

As a second crop, watermelons (Citrullus vulgaris, Crimson sweet) were grown in 2003 and 2004 in the Sanliurfa-Harran Plain in southeastern Turkey to determine the effect of preharvest water stress on fruit yield, quality (i.e., soluble solids contents and fruit size), leaf temperature, and some other physiological parameters. Preharvest drip irrigation treatments included (1) complete irrigation cutoff, dry (D); (2) full irrigation based on replenishment of soil water depleted from 0 to $90\mathrm{cm}$ soil profile (C); (3) 75% full irrigation (IR1); (4) 50% full irrigation (IR2); and (5) 25% full irrigation (IR3) with 3-day irrigation interval. Treatment plots received the same level of irrigation water until the fruit formation stage, except for Treatment D. Then, different water stress levels were imposed on treatment plots. Irrigation water applied to the five respective treatments were 636, 511, 395, 245, and $120\mathrm{mm}$ in 2003 and 648, 516, 403, 252, and $127\mathrm{mm}$ in 2004. Results indicated that fruit yield was significantly lowered by reduced water rates. The seasonal average yield response factor $\left(k_y\right)$ for both years was 1.0, but it was 0.97 for 2003 and 0.98 for 2004. The highest marketable fruit yield, obtained from treatment C, was $32.4\mathrm{Mg}{\mathrm{ha}}^{-1}$ in 2003 and $37.1\mathrm{Mg}{\mathrm{ha}}^{-1}$ in 2004. D, IR2, and IR3 treatments reduced most measured parameters, except for soluble solids contents (SSC). Both the fruit size and SSC were significantly affected by late-season irrigation management; individual fruit weights were significantly reduced, whereas SSC increased in the IR2 and IR3 treatments compared to the control values. The writers’ results clearly indicated that reduced preharvest irrigation was detrimental. Water use efficiency (WUE) was significantly affected by irrigation treatments. Even a 25% reduction in the irrigation amount caused a 15% reduction in marketable yield. This indicates that deficit irrigation in the ripening stage significantly increased water use efficiency. The study demonstrated that a moderate deficit irrigation, which is replenishment up to 50% of soil water depleted in the root zone, can be successfully used to improve WUE under semiarid climatic conditions.

The success of irrigation system operation and planning depends on the quantification of supply and demand and equitable distribution of supply to meet the demand if possible, or to minimize the gap between the supply and demand. Most of the irrigation literature mainly focuses on the demand and distribution aspects only. In addition, irrigation projects that receive water from a reservoir can be challenging to manage as annual fluctuations in runoff from the reservoir’s catchment can have considerable impact on the irrigation management strategy. This study focuses on the development of an integrated reservoir-based canal irrigation model (IRCIM) that includes catchment hydrologic modeling, reservoir water balance, command hydrologic modeling, and a rotational canal irrigation management system. The front end of the IRCIM is developed in Visual Basic 6.0, whereas the back-end coding is done in C language. The graphical user interface is the most important feature of the model, as it provides a better interaction between the model and its user. The IRCIM has a modular structure that consists of three modules, viz., catchment module, reservoir module, and crop water demand module. The catchment module predicts daily runoff from the catchment that inflows to the reservoir. Depending on the data availability, this module is provided with the flexibility of choosing between the Soil Conservation Service’s curve number method combined with the Muskingum routing technique, and an artificial neural network technique using the Levenberg–Marquardt algorithm. The reservoir module is based on conservation of mass approach, and results in daily reservoir storage. The crop water demand module is comprised of water-balance models for both paddy and field crops. The irrigation management system serves as the program flow controller for the model and runs the required module when needed. For postseason evaluation of the irrigation system, performance indicators such as adequacy, efficiency, equity, and dependability are used. In a companion paper, the model is applied for Kangsabati Irrigation Project, West Bengal, India.

In a companion paper, development of an integrated reservoir-based canal irrigation model (IRCIM) was described. This developed model combines catchment hydrological modeling, reservoir water balance, command hydrological modeling, and a simple canal hydraulic simulation through a rotational irrigation management system, and simulates the whole system as a single unit to ensure equitable distribution of supply to meet the demand if possible, or, to minimize the gap between the supply and demand. In this paper, the developed model was applied to Kangsabati Irrigation Project, West Bengal, India, as a case study. Results showed that IRCIM successfully simulated the operation of the test reservoir after proper calibration and was able to determine better delivery schedules than that actually practiced. The best delivery schedule determined by IRCIM improved the performance of the test irrigation project considerably over the actual delivery schedule for most of the simulation years. Based on these yearly results, a year-independent alternative delivery schedule was also proposed which could be followed mechanically without a manager’s expertise or experience on the particular irrigation project. It was also shown that IRCIM could be used successfully both modulewise or in an integrated way depending on the requirement of the irrigation manager for efficient operation of any reservoir-based canal irrigation systems either for preseason planning of allocation schedules based on hydrologic and hydraulic simulations or for postseason evaluation of the system performance.

The Middle Rio Grande Conservancy District (MRGCD) was officially founded in the 1920s, but it may well be the oldest operating irrigation system in North America. Currently the MRGCD serves about 22,300 ha of irrigated land and provides additional benefits to the Middle Rio Grande MRG Valley by providing proper soil drainage and protection against flooding. In recent years, the demand for water in the MRG Valley has increased drastically due to explosive population growth, expanding industry, and water allocated for environmental and ecological concerns, which include two federally listed endangered species—the silvery minnow (Hybognathus amarus) and the southwestern willow fly catcher (Empidonax traillii extimus). In response to the call for more efficient water use, the MRGCD embarked on a program of irrigation system modernization with supervisory control and data acquisition (SCADA) incorporation. Over the past few years, the MRGCD has developed a SCADA system focused on improving water use efficiency throughout the MRG Valley. This paper examines the five components of the system and how each component was developed and incorporated in the overall SCADA system. The SCADA system and related improvements in operational practices have reduced MRGCD river diversions from $7.4\times {10}^8{\mathrm{m}}^3∕\text{year}$ a decade ago to an average of $4.3172\times {10}^8{\mathrm{m}}^3∕\text{year}$ over the last $3\text{years}$ .

Water is the lifeblood of the American West and the foundation of its economy, but it remains its scarcest resource. The explosive population growth in western United States, the emerging additional need for water for environmental uses, and the national importance of the domestic food production are driving major conflicts between these competing water uses. The case of the Middle Rio Grande illustrates the problem very well. The river is the ecological backbone of the Chihuahuan Desert region in the western United States, and supports its dynamic and diverse ecology, including the fish and wildlife habitat. The Rio Grande Silvery Minnow is federally listed as an endangered species, and the irrigated agriculture in the Middle Rio Grande has come under increasing pressure to reduce its water consumption and maintain the desired level of service to its water users. This paper will present the writers ongoing research on options to make irrigation system operations more efficient in the Middle Rio Grande Conservancy District (MRGCD). Specifically, it will describe formulation and implementation of a decision support system (DSS) that can assist the MRGCD managers to more efficiently plan and implement their water delivery operations, thereby reducing river diversions. The MRGCD DSS uses linear programming to find an optimum water delivery schedule for canal service areas in the MRGCD irrigation system. The computer model is presently formulated along with the related data sets for two of the four divisions in the MRGCD. For the past $3\text{years}$ , the model has been validated in the field and the evaluation indicates that the model recommendations are realistic and represent current management practices. The future plans are to complete the data files for the irrigation networks in the remaining two divisions and concurrently help the MRGCD implement the DSS to guide water delivery operation.

This technical paper presents analytical expressions to estimate the probability function of head losses in any path of an on-demand branched irrigation network. They are developed for estimating the probability of pressure deficit of a given magnitude at any hydrant. They are also useful for examining the probability of a power deficit at a pumping station designed to guarantee service to a hydrant, as well as the head characteristic curve of the distribution system linked to a definite probability. All this quantified information is useful for decision making on network design and performance. The probabilities calculated with the developed expressions can be taken as complementary or alternative concepts to Clément’s classical design flow method, which is taken here as a benchmark for comparisons. Illustrative examples of network designs are presented to validate the proposed expressions. The least cost design solutions using Clément’s design flows are compared with design solutions here obtained to get the same probability of pressure deficit at the most unfavorable hydrants. The new solutions are less expensive because the flow constraint can be avoided.

Riparian buffers are commonly promoted to protect stream water quality. A common conceptual assumption is that buffers “intercept” and treat upland runoff. As a shift in paradigm, it is proposed instead that riparian buffers should be recognized as the parts of the landscape that most frequently generate storm runoff. Thus, water quality can be protected from contaminated storm runoff by disassociating riparian buffers from potentially polluting activities. This paper reviews and synthesizes some simple engineering approaches that can be used to delineate riparian buffers for rural watersheds based on risk of generating runoff. Although reference is made to specific future research that may improve the proposed methods for delineating riparian buffers, the approaches described here provide planners and engineers with a set of currently available scientifically defensible tools. It is recommended that planners and engineers use available rainfall and stream discharge data to parameterize the buffer-sizing equations and use variable-width buffers, based on a topographic index, to achieve a realistic representation of runoff generating areas.

The purpose of this research was to evaluate peak runoff control as a water protection method to reduce sediment and nutrient loads. Increased eutrophication of surface waters and risk of floods demands cost effective methods to reduce pollutant input and risks of flooding. With the peak runoff control it is possible to cut the main peaks and store the runoff water temporarily in ditches. The method decreases the suspended solids (SS) and nutrient loads by reducing flow velocities, and improving the settling of sediment particles. The method was tested in two heavily drained adjacent peat harvesting areas suffering considerable erosion. The peak flows were cut by 27–87%, the SS load by 61–94%, the total nitrogen $\left({\mathrm{N}}_{\mathrm{tot}}\right)$ by 45–91%, and the total phosphorus $\left({\mathrm{P}}_{\mathrm{tot}}\right)$ load by 47–88%. The peak runoff control method operated most effectively during extreme events when most of the SS load is transported. A detailed particle analysis of runoff water showed that water detention reduced the median particle size of SS load as the largest particles settle. The results clearly indicate that the peak runoff control is an effective method to control the sediment loads and peak flows from peatland drainage.

The pollutant removal efficiency of a bioretention area and a level spreader-grass filter strip implemented at North Carolina highway facilities was assessed. The assessment consisted of monitoring inflow, outflow, and on-site rainfall for at least 13 storm events. Monitoring included continuous discharge measurement and collecting and analyzing flow-proportional samples for each event. All samples were analyzed for solids, turbidity, and nitrogen and phosphorus forms and selected samples were analyzed for metals. The level spreader-grass filter strip had the best overall efficiency with load reduction efficiencies in all pollutants ranging from 24 to 83% and the highest reduction for total suspended solids (TSS). Much of the efficiency of this best management practice can be attributed to the 49% reduction in runoff volume from inflow to outflow. Pollutant reduction efficiencies for the bioretention area ranged from $-254$ to 76% with the highest reduction for TSS. The lowest or large negative efficiency was for $\text{nitrate}+\text{nitrite}$ nitrogen $(\mathrm{N}{\mathrm{O}}_{2+3}–\mathrm{N})$ . The increase in $\mathrm{N}{\mathrm{O}}_{2+3}–\mathrm{N}$ likely resulted from a combination of nitrogen additions within the cell and conversion of other forms of nitrogen to $\mathrm{N}{\mathrm{O}}_{2+3}–\mathrm{N}$ . Statistical analyses suggested that all of the mass reductions for the grass filter strip and many of those for the bioretention area were significant.

The hydraulic behavior of several continuous transverse gully grates is studied. Their use is common in some urban or impervious areas (squares, airport pavements, parks, pedestrian areas, etc.) where isolated inlets turn out to be ineffective in collecting the whole runoff into the sewer system during a storm event. Normally, manufacturers of such structures provide information about the bearing capacity, but little concerning their hydraulic behavior. Some grates with various widths were tested at the Technical University of Catalonia hydraulic laboratory for different approach flows and a large set of longitudinal slopes. Experimental equations were obtained to relate hydraulic efficiency of these structures to some relevant flow parameters such as the Froude number and the hydraulic depth. The first equation achieved may be used as a first approach to design a surface drainage system considering a constant circulating flow, whereas the second expression does not depend on flow values and could be used in storm-water and wastewater software packages to design surface drainage systems and for dual drainage modeling.

We report on a curious result related to the computation of the asymptotic depth in rough compound channels by one-dimensional approaches. Such approaches, which are widely used in practice, utilize one of a number of well-established methods for estimating the equivalent composite/compound roughness. It was found that many of these methods yield predictions of the asymptotic water depth which erroneously depend on the initial, control, depth. Only one of the methods examined was found not to exhibit this unsatisfactory behavior. We explain the results by analysis of the governing equations.

Mechanical vibration of the grass and crop weighing lysimeters, located at the University of California West Side Field Research and Extension Station at Five Points, Calif. generated noise in lysimeter mass measurements and reduced the quality of evapotranspiration (ET) data. The estimated power spectral density (PSD) for grass lysimeter mass data acquired at $1.3\mathrm{ms}$ intervals contained a large peak at $11\mathrm{Hz}$ . Crop lysimeter data produced similar peaks at frequencies greater than $1\mathrm{Hz}$ . An effective method for eliminating this noise source is arithmetic averaging of the data, which should be acquired sufficiently rapidly to avoid aliasing. The PSD also increased with decreasing frequency in the range $1.0–0.1\mathrm{Hz}$ . This noise was addressed by Savitsky–Golay (SG) filtering using 7-, 11-, and 15-point filters. Each filter was applied to the same data set consisting of 2,560 measurements taken during a $1\text{-}\min$ interval every $10\min$ over a $26.3\text{-}\mathrm{h}$ period. Noise reduction factors, defined as the ratio of standard deviation of filtered lysimeter mass to standard deviation of unfiltered mean values of lysimeter mass for subsequences of the same data, were 0.90, 0.88, and 0.86 for the 7-, 11-, and 15-point filters, respectively. For the daytime data only, the factors were 0.88, 0.85, and 0.83. The SG filters were more effective during daytime when most of the lysimeter ET occurs. These methods are simple enough to be programmed into commercially available dataloggers for real time filtering. Hourly averages of the standard deviations of lysimeter mass measurements bear a distinct nonlinear relationship to hourly mean wind speed confirming earlier suppositions that wind loading causes noise in counterbalanced weighing lysimeters.

Four standard design storms (called Types 1, 1A, 2, and 3) developed by the National Resource Conservation Service (NRCS) are used widely throughout the United States for hydrological design of flood control structures and storm-water best management practices. The $24\text{-}\mathrm{h}$ rainfall patterns are intended for use in catchments with areas of $250{\mathrm{km}}^2$ or less, and they are considered applicable to storms of any average recurrence interval. Presented as ratios of accumulated rainfall depth to the total $24\text{-}\mathrm{h}$ rainfall depth at $6\min$ intervals, interpolation of the tabulated values usually is needed to obtain rainfall intensities at desired storm times. A mathematical formulation of rainfall intensity consisting of two exponential terms and a constant term is fit to each of the four distributions, and optimal values of the model coefficients are found. The formula reproduces closely all of the four NRCS $24\text{-}\mathrm{h}$ design storms, and can be used to extract shorter duration subsets of the $24\text{-}\mathrm{h}$ rainfall patterns in an uncomplicated way.

It has been a long-standing concern to decide if a channel should be designed to have the highest hydraulic efficiency or the least cost. In this study, a large amount of channel construction costs were reviewed and analyzed to derive the channel construction cost function as the sum of the costs for the land acquisition of the channel’s alignment, lining material for the channel’s cross section, and earth excavation for the channel’s depth. Case studies conducted in this technical note indicate that the differences between the least-cost and most efficient cross sections are closely related to the channel lining to land acquisition cost ratio. When the lining to land unit cost ratio vanishes, the difference between these two cross sections is diminished. As revealed by the cost data, the least-cost channel section tends to be deeper if the land cost is much higher than the lining cost. This trade-off was incorporated into the normalized equation to provide direct solutions to the least-cost channel cross section. The normalization of the least-cost equations allows this approach to be transferred to other regions when the local cost data are available.

A kernel method is proposed for calculating transient rate and cumulative volume of well discharge under constant drawdown. The new method can also be used for obtaining the drawdown (in pressure head) in the aquifer at some distance away from the well. Employing the new method, an optimization method is used to estimate the aquifer parameters from transient well discharge or drawdown in the aquifer pressure head. The proposed method can also be used to model the recovery of drawdown (in aquifer pressure head) after the plug-in of the well.

A ramp kernel method is proposed for accurately calculating the drawdown due to any temporal variation in pumping discharge. The use of the ramp kernels assumes the linear variation between the two consecutive measured pumping discharges. The prior studies assume a rectangular variation between the two consecutive measured pumping discharges. In the rectangular variation, a uniform pumping rate is assumed during a time span. An analytical equation for calculating the ramp kernel is derived. An optimization method is used with the proposed ramp kernels for inversely estimating the aquifer parameters from drawdown due to an arbitrary unsteady pumping discharge. Unlike the prior methods, the proposed method accurately identifies the parameters even when the sampling interval for the drawdown and pumping discharge is longer than that needed for assuming a linear variation. The proposed method outperforms the prior method. Application of the proposed method is illustrated using examples.