Journal of Irrigation and Drainage Engineering

Beginning in January 1992, the Bureau of Reclamation (Reclamation) and the US Geological Survey (USGS) formulated plans for the Watershed and River Systems Management Program—a cooperative interagency effort to develop and implement flexible and robust river basin management tools for the benefit of managers and decision makers using a data centered approach. In addition to Reclamation and the USGS, a number of other agencies and universities have made substantial contributions to the success of the program. The result has been the need driven research and development of state-of-the-art technology which benefits water managers and technical specialists in many river basins.

The hydrologic modeling inventory developed at the Bureau of Reclamation and posted at its website ⟨http://www.usbr.gov/pmts/rivers/hmi⟩ is described. The inventory comprises a large number of state-of-the-art watershed models developed by government (federal, state, and local) agencies, universities, and private companies in the United States and elsewhere. This inventory is among the first of its kind and is useful not only for modelers but water resources planners and managers.

In recent years, reservoir management considerations have expanded to include environmental and recreational objectives, many of which are often difficult to quantify. With a larger set of operational objectives comes the need to identify tradeoffs and uncertainties among the various objectives. Uncertainty modeling may contribute to better reservoir management by identifying and quantifying the sources of significant uncertainty in predicting reservoir and river conditions that affect environmental habitats and recreational conditions. We implement a first-order, second-moment algorithm in RIVERWARE, an object-oriented river and reservoir modeling environment. The method is developed and applied to a case study from the lower Colorado River, where a preexisting deterministic model is used for reservoir operations and planning. The case study involves evaluation of uncertainties associated with prescribed reservoir pool elevations for purposes of recovering endangered fish species. Comparison of historical forecasts with observed data can provide managers with insight into operational policies that result in greater system uncertainty. Identifying these sources of uncertainty can guide managers in the development of future operational guidelines.

SAMS is a specialized software that has been developed for analyzing, modeling, and generating synthetic samples of hydrologic and water resources time series such as monthly streamflows. The 2003 version of SAMS provides enhanced technical capabilities from the earlier versions of the software. The graphical user interface and the mechanisms for handling the data have been entirely rewritten in MS Visual C++. As a result SAMS-2003 is easier to use and easier to update and maintain. In addition, substantial changes and restructuring have been made to enhance the modeling and data generation capabilities. The package provides many menu option windows that focus on three primary application modules—statistical analysis of data, fitting of a stochastic model (including parameter estimation and testing), and generating synthetic series. SAMS has the capability of analyzing and modeling single site and multisite annual and seasonal data such as monthly and weekly streamflows based on a number of single site and multisite stochastic models, and aggregation and disaggregation modeling schemes. The models are then utilized for generating synthetic data. Results from the various computations, e.g., the generated samples, can be presented in graphical and tabular forms and, if desired, saved to an output file. Some illustrations are provided to demonstrate the improved technical capabilities of the program using flow data of the Colorado River system.

This paper presents a genetic algorithm (GA) model for obtaining an optimal operating policy and optimal crop water allocations from an irrigation reservoir. The objective is to maximize the sum of the relative yields from all crops in the irrigated area. The model takes into account reservoir inflow, rainfall on the irrigated area, intraseasonal competition for water among multiple crops, the soil moisture dynamics in each cropped area, the heterogeneous nature of soils, and crop response to the level of irrigation applied. The model is applied to the Malaprabha single-purpose irrigation reservoir in Karnataka State, India. The optimal operating policy obtained using the GA is similar to that obtained by linear programming. This model can be used for optimal utilization of the available water resources of any reservoir system to obtain maximum benefits.

A three-step computational model for the optimal weekly interseasonal operation of a multipurpose (irrigation, environmental, domestic/industrial) reservoir is developed. Environmental and domestic/industrial uses are evaluated and considered as priority uses that induce deficit irrigation conditions. The spatiotemporal variability of the irrigation water demand at the basin level is accounted for. The objective is the maximization of the interseasonal agricultural profitability at the basin level. The optimal allocation process solves the competition for water on different temporal scales (weekly, seasonal, and interseasonal) and on different spatial scales (in basins among irrigation areas and in irrigation areas among crops). The three steps are simulation model operating at the soil-crop unit level, optimization model operating at the multicrop area level, and optimization model operating at the basin level. This consists of parametric dynamic programming for which an analytical objective function was defined and an analytical solution was determined. This solution replaces the iterative procedure, so that it is possible to account for all the variables without running into the “curse of dimensionality” problem. The environmental use allocation is expressed as a function of a parameter, the variations of which give different environmental protection levels. The validation case study emphasizes the importance of considering the spatiotemporal variability of the demand. This is consistent with the “computationally tractable” model algorithm.

The feasibility of automatically controlling water levels and deliveries on the Salt River Project (SRP) canal system through computer-based algorithms is being investigated. The proposed control system automates and enhances functions already performed by SRP operators, namely feedforward routing of scheduled demand changes, feedback control of downstream water levels, and flow control at check structures. Performance of the control system was tested with unsteady flow simulation. Test scenarios were defined by the operators for a 30 km, four-pool canal reach. The tests considered the effect of imperfect knowledge of check gate head-discharge relationships. The combined feedback-feedforward controller easily kept water level deviations close to the target when dealing with routine, scheduled flow changes. Those same routine changes, when unscheduled, were handled effectively by the feedback controller alone. The combined system had greater difficulty in dealing with large demand changes, especially if unscheduled. Because feedback flow changes are computed independently of feedforward changes, the feedback controller tends to counteract feedforward control actions. The effect is unimportant when dealing with routine flow changes but is more significant when dealing with large changes, especially in cases where the demand change cannot be fully anticipated.

A method is presented that uses continuous soil moisture measurements and hourly reference evapotranspiration data to estimate a soil hydraulic factor $\left(\beta \right)$ for modeling soil evaporation. The $\beta$ factor is used to assess the end of the energy limited soil evaporation phase (Stage 1) and the evaporation rate during the soil hydraulic limited phase (Stage 2) of a two-stage soil evaporation model. A previously developed and tested method to determine $\beta$ uses an energy balance approach with sensible heat flux density estimated using the surface renewal method to obtain the continuous soil evaporation. A new method is presented, which uses a hydroprobe soil moisture measuring device to estimate the continuous soil evaporation. The estimation of evaporation with soil moisture sensors was simpler and less expensive when compared to the energy balance technique. The methods, evaluated in two field experiments, showed good agreement with evaporation data. Using the evaporation model and $\beta$ derived from either method provided a good estimate of measured soil evaporation. Modeled daily soil evaporation, using either energy balance or soil measurements to obtain $\beta$ , gave a root-mean-square error of 0.6 $\mathrm{mm}{\text{day}}^{-1}$ when compared with soil evaporation measured using the energy balance method. When daily soil evaporation from soil moisture measurements was compared with soil evaporation estimated from energy balance measurements, the root-mean-square error was 1.3 $\mathrm{mm}{\text{day}}^{-1}$ . Direct soil monitoring method had bigger error, but the method is less costly.

Lagoon effluent is routinely applied to agricultural fields as fertilizer to utilize nutrients derived from animal manures. In humid regions, effluent is also applied to fields in order to manage the lagoon stage within acceptable levels. To minimize the risk of applied nutrients being transported to surface waters, best management practices such as vegetative buffers and controlled drainage are often recommended. This paper presents the results of a field study to evaluate the effectiveness of controlled drainage and vegetative buffers in reducing the transport of wastewater nutrients from land application fields. Swine lagoon effluent was spray irrigated to Bermudagrass fields drained by a parallel ditch system. Drainage outflow was monitored continuously for a 3 year period. Vegetative buffers reduced the average concentration of phosphorus by about 30%, but the average concentration of nitrogen was not affected. Controlled drainage resulted in higher individual event nitrogen concentrations, which were due primarily to irrigation onto fields at times when they were too wet to be effectively irrigated. In most cases, the concentration of total N in drainage was comparable to the values observed from other agricultural fields receiving inorganic fertilizer. However, the nitrogen was mainly in the ammonium form rather than nitrate, which could pose greater environmental risk to some fish and other aquatic species in surface waters. The peak concentrations were higher for the controlled drainage treatments than for conventional drainage. The loss of nitrogen in drainage water accounted for roughly 10% of the amount applied (8% on the conventional drainage treatments and 11% on the controlled drainage treatments). On two plots (one controlled, one conventional), more than 40% of the total N transport over the 3 year study period was associated with one extended flow event when wastewater was applied several times while the water table was near the surface. These poorly scheduled irrigations onto already wet fields resulted in as much N and P transport in one event as occurred during the remainder of the study when irrigation was properly scheduled onto dry fields. These observations suggest that irrigation scheduling and proper management were more important to water quality than remedial actions such as controlled drainage or vegetative buffers.

This paper presents an investigation of the performance of the hydraulic and sediment removal of a flushing system in a detention basin. A hydraulic criterion for the design of the flushing system is proposed. An equation for the maximum height of the flushing wave front as a function of the distance from the gate, the initial water depth in the chamber, and the chamber length is proposed. The Lauber and Hager equation for the maximum velocity of a flushing wave is also verified. Effective removal of sediment particles on the bed is a direct function of the bed shear stress generated by the flushing flow. This study reveals that the bed shear stress on the channel bed induced by the flushing flow can be attributed to the hydrostatic pressure, the flow acceleration, and the convection-induced momentum. The shear stress associated with fluid distortion and the turbulent viscosity may be neglected. Significant error would occur if the hydrostatic pressure component were used as an estimate of the bed shear stress on a mild slope channel. The energy slope method may provide an overestimate of the bed shear stress. Finally, an appropriate equation to evaluate the maximum bed shear stress is proposed.

Dimensional analysis was used to obtain stage–discharge relationships under submerged and free flow conditions in radial gates to develop a management tool. Experimental data from a laboratory flume and the indicial method of dimensional analysis were used for this purpose. The resulting equation relates the discharge (or critical depth) to upstream and downstream water depth and gate opening. These equations were then validated by experimental data obtained from field radial gates and compared with the conventional gate equation. Results showed that there was a good agreement between dimensionless equations and field and laboratory data under submerged or free flow conditions. Dimensionless equations are more general and accurate than the conventional ones when there is not an accurate estimation of discharge coefficients.

A procedure called water wiping is developed to measure the amount of water intercepted by the canopy of winter wheat under sprinkler irrigation. Macromolecule bibulous materials with high water absorption is used to collect sprinkler water intercepted by winter wheat canopy by wiping water from leaves, sheathes, heads, and stems. A procedure is developed for application and verified using field experiments. The results show that this method is rational and applicable. This method could be used to measure canopy interception of other crops with small leaves and short heights.