Journal of Irrigation and Drainage Engineering

In California, daily crop evapotranspiration (${\mathit{ET}}_c$) is commonly estimated using near-real-time, standardized reference evapotranspiration (${\mathit{ET}}_o$) calculated from ground-based meteorological data and crop coefficient ($K_c$) values that adjust for the difference between ${\mathit{ET}}_o$ and ${\mathit{ET}}_c$. However, using ${\mathit{ET}}_o$ calculated from forecast rather than near-real-time meteorological data provides more timely information to growers, farm managers, urban water users, irrigation practitioners, and water purveyors to anticipate water demand for the upcoming days. This is particularly important for water allocation and delivery planning and for irrigation scheduling decisions. Forecast ${\mathit{ET}}_o$ is also relevant for scientific research for developing methods and tools enabling more resource-efficient water use for agricultural production and urban landscapes. Verifying the reliability of ${\mathit{ET}}_o$ forecast models for various climatic conditions is crucial for promoting the broad adoption and use of ${\mathit{ET}}_o$ predictions for weather-based adaptive water management and prospective irrigation scheduling. The US National Weather Service (NWS) has released a product called forecast reference evapotranspiration (FRET) that provides ${\mathit{ET}}_o$ forecasts at a 2.5-km grid resolution for the entire continental US. In this study, comparisons were made between ${\mathit{ET}}_o$ forecasts from FRET and observed ${\mathit{ET}}_o$ values from the California Irrigation Management Information System (CIMIS) for a total of 78 days during the peak irrigation water demand period of 2019, which corresponded to the midseason period for major crops. FRET ${\mathit{ET}}_o$ forecasts and CIMIS ${\mathit{ET}}_o$ observations (calculated from measured weather parameters) were compared for 15 CIMIS station locations to represent a variety of weather conditions of some major agricultural production and urban areas in California. Air temperature, dew point temperature, wind speed, and solar radiation data were collected from NWS and CIMIS and analyzed to assess the accuracy of predicted weather variables and FRET ${\mathit{ET}}_o$ forecasts. The FRET data consisted of 1, 3, 5, and 7-day forecasts of weather parameters and calculated ${\mathit{ET}}_o$ values; these were compared with the corresponding observed daily weather and ${\mathit{ET}}_o$ data from CIMIS in order to statistically evaluate FRET performance. The comparison among forecast and measured weather variables revealed a good match for maximum air temperature ($R^2$ between 0.98 and 1.00), minimum air temperature ($R^2>0.91$), dew point temperature ($R^2$ between 0.7 and 1.00), and wind speed ($R^2$ between 0.66 and 0.99); less accurate results were obtained for solar radiation ($R^2$ between 0.21 and 0.87). The analysis also showed a good correlation between FRET ${\mathit{ET}}_o$ forecast data and observed CIMIS ${\mathit{ET}}_o$ data ($R^2$ between 0.93 and 1.00 and root mean square error (RMSE) was less than $1\mathrm{mm}·{\mathrm{day}}^{-1}$) for the majority of the selected stations, with some differences that were likely due to the climatic conditions of specific locations. This suggests that FRET ${\mathit{ET}}_o$ forecasts provide reliable information for predicting near-future water demand and improving irrigation water management in California. The comparisons showed a good match for most of the 15 CIMIS stations, and the FRET model may potentially provide accurate ${\mathit{ET}}_o$ forecasts in similar semiarid and subhumid areas elsewhere. Weekly irrigation schedule examples are provided in the Appendix to illustrate the use of FRET ${\mathit{ET}}_o$ forecasts in combination with site-specific information on soil hydraulic properties and irrigation system performance for prospective irrigation scheduling of some specialty crops and urban landscapes. The information provided in this article can help improve the water management efficiency of high-frequency agricultural irrigation systems and urban sprinkler systems in California and other locations with similar climates. It also offers a less expensive method to obtain ${\mathit{ET}}_o$ data in countries that do not have ${\mathit{ET}}_o$ station networks, because it offers an alternative to installing and maintaining ${\mathit{ET}}_o$ stations in agricultural and urban areas where it is difficult to find acceptable surfaces for developing reliable ${\mathit{ET}}_o$ information.

Concrete linings of field canals are seriously damaged by frost heave in the north of China. However, the mechanism causing lining damage is too complex to be described quantitatively, and present models are insufficient in considering soil–lining interaction. Based on mechanical analysis and the direct shear test, the restrictive relationship between the freezing soil and lining is introduced as a key point to quantitatively simulate the process of lining damage. Heat convection, solar radiation, and a moving water table boundary are also incorporated in the present model to simulate boundary conditions with daily climate data. Finally, two cases in the Hetao irrigation district are simulated. The developed model agrees with experiment data and can reflect the failure characteristics of lining. The results show: (1) the contact interface between lining and freezing soil will slide early in the freezing season, (2) reducing the freezing strength or weakening the restrictive relationship between the lining and freezing soil can reduce the maximum stress of the lining, (3) new lining structures with shapes like parabola and catenary perform better than a round-bottom-triangular (RT) shape because of a gentler side slope, and (4) large amounts of migration water accumulate and freeze beneath north (shady) slopes and cause a high damage risk for the lining. This paper can provide a reference for the further study of efficient and economical engineering methods for solving the lining damage problem.

Accurate flow rate prediction is essential to analyze flood control, sediment transport, riverbank protection, and so forth. The flow rate distribution becomes even more complicated in compound channels due to the momentum transfer between different subsections across the width of the channel. Conventional channel division methods estimate flow distribution at the main channel and floodplains by assuming a division line with zero apparent shear stress. The article attempts to develop a model to calculate the percentage of discharge in the main channel $(\%Q_{mc})$ using techniques such as Group Method of Data Handling—Neural Network (GMDH-NN) and gene-expression programming (GEP) by incorporating the effects of various geometric and hydraulic parameters. The paper proposes a modified channel division method with a variable-inclined interface, with zero apparent shear force distribution at the channel subsections according to the statistical indices employed to assess these models’ performance in predicting $\%Q_{mc}$. This variable-inclined interface changes its slope according to the channel parameters. The model’s effectiveness is verified by validating with experimental observations by conventional analytical methods.

Self-formed shape and energy loss taking place at the transition of alluvial canals were studied. Two trapezoidal erodible canals were modeled along with a sudden contraction in a laboratory flume. Experiments were performed under steady flow conditions for almost-uniform coarse sand with average grain sizes of 1.2, 0.91, and 0.77 mm and flow rates ranging from 0.0001 to $0.0025{\mathrm{m}}^3/\mathrm{s}$. The results show that the ultimate self-formed warped transition can be represented by an exponential relation that depends on average grain size and flow rate. For a constant flow rate, the length of transition decreases as the grain size increases, whereas for a constant grain size it increases with increasing flow rate, and the minimum energy loss is obtained at the threshold condition.

Stormwater management is necessary to protect surface waters from pollutants, and significant amounts of time and money are being expended to purchase and install sediment control logs for this purpose. Testing to compare new innovations in sediment control log filter media and uses has been done; however, more is needed. Whereas testing has traditionally been done using open-channel flumes, a large-scale constant head permeameter was used in this study, and its measurements were compared with testing results from open-channel flume measurements to indicate that this testing method is viable, if not a preferable, alternative. A nonlinear relationship involving the specific discharge was determined in a variety of filter media, including straw, coir, wood fiber, rock, and wood compost. The nonlinear relationship suggests that a nonlaminar flow is occurring within the media. The height of the seepage emerging from the downstream face of a sediment control log was also demonstrated to be a critical measured parameter if an open-channel flume is used as a testing apparatus. This study also included sediment capture testing and revealed that sediment control logs are capable of removing 72% to 92% of suspended sediments by weight, mostly through sedimentation, but with as much as 15% removal through filtration, depending on the media type.

Piano Key Weirs (PKWs) are often preferred over other spillways for the dam rehabilitation due to high discharging capacity. The present study investigates scour downstream of three cycles of PKWs with and without solid apron under both free and submerged flow conditions. The scour formations downstream of the inlet and outlet keys were investigated by varying discharges and tail water depths. Three different types of aprons were used under varied discharges and tail water depths. Falling and impinging jets emanating from inlet and outlet keys were noted as being responsible for the formation of ridge and dip, respectively. The maximum depth of scour was 40%–80% of the total weir height under different discharges. For high submergence, negligible scour development was reported. The average reduction in the scour depth with a solid apron lies in the 60%–80% range. Empirical equations were developed using a least square technique for the computation of maximum scour depth for both the conditions, that is, with and without a solid apron. Statistical and graphical analysis indicates better conformity of the proposed equation with the previous investigation. Sensitivity analysis indicates that the ratio of tailwater depth to the median size of a sediment particle ($y_t/d_{\mathit{50}}$) and the ratio of the crest length to the width of the weir ($\mathit{L}/\mathit{W}$) are the most sensible parameters affecting maximum scour with and without a solid apron, respectively.

Soil erosion prevention and management represents a major environmental challenge faced by many highway construction projects. This study analyzed sustainable improvements to current standard procedures for final grade turfgrass establishment on disturbed soils. Using a series of greenhouse studies, compost and compost–topsoil blends with and without straw mulching were compared with a standard topsoil–straw–fertilizer practice in terms of their ability to reduce soil and nutrient loss and improve the rate of green vegetation (GV) establishment at a variety of slope ratios. Straw mulching significantly improved GV establishment ($64\%–93\%$), reduced runoff volume ($22\%–99\%$), and reduced sediment and nutrient mass export ($71\%–99\%$ for sediment, $71\%–92\%$ for nitrogen, and $66\%–99\%$ for phosphorus). These reductions and improvements were attributed largely to the physical barrier offered by the straw mulch layer. This layer improved soil water storage through reduced evaporation, reduced rainfall impact, and increased media surface roughness, which resulted in reduced runoff velocity, soil splash, and compaction, and increased available water for plant uptake. Compost amendment to the topsoil standard material with straw mulching in general increased hydraulic conductivity and improved soil aggregation and stability, which reduced the total runoff volume ($13\%–59\%$), sediment mass ($64\%–98\%$), and nutrient mass export ($6\%–82\%$ nitrogen and $4\%–76\%$ phosphorus). As slope ratio increased, export of runoff volume, sediment, and nutrients statistically increased, whereas GV decreased.