Journal of Irrigation and Drainage Engineering

Competing demands for scarce water supplies in irrigated alluvial valleys can lead to conflicts between disparate uses, resulting in an increased risk of restrictions on agricultural diversions. A tool for understanding the impacts of irrigation diversions on natural stream systems at the tributary scale is needed to evaluate solutions that protect environmental flow requirements for endangered and threatened aquatic species while maintaining irrigation water security. A geospatially referenced decision support system (geo-DSS) coupling a fine-scale [$1/4$ Hydrologic Rainfall Analysis Project (HRAP) or 1 km] gridded hydrometeorological model (HL-RDHM) with a GIS-based river basin management model (GeoMODSIM) is developed for irrigated stream-aquifer systems. In this proof-of-concept implementation, the geo-DSS is demonstrated on a representative tributary within the Russian River Basin in the Northern Coastal region of California with extensive wine grape vineyard acreage for an average water year using a daily time step. Results indicate that commonly used management practices that rely on direct stream diversions and on-stream ponds for irrigation can have severe negative impacts on instream flow rates by impeding the migration of endangered coho salmon and other species. Through the application of the geo-DSS, improved management practices such as the use of off-stream agricultural ponds are able to meet irrigation demands while satisfying minimum environmental bypass flow restrictions along with the determination of ideal sizes and locations for supplemental off-stream storage.

A block ramp is an environmentally friendly stream restoration structure consisting of a base material of stone with minimal negative environmental impact. This not only decreases riverbed shear stress but also increases the flow resistance, thus reducing excess kinetic energy of the flow. This study used two mathematical models that were developed in a dimensionless form for smooth and rough-bed ramps. The models were calibrated and validated by two sets of experimental tests. A total of 308 experimental runs were done with eight different ramp slopes and six different gravel material sizes. The experimental results indicated that an increase in the relative roughness enhances energy dissipation. Additionally, energy dissipation increases along with an increase of ramp slope. Using a gene-expression programming soft computing model, two mathematical models were developed to estimate energy dissipation on smooth and rough-bed ramps. Additionally, the energy-loss performance of two configurations of interlocked and dumped blocks ramps was compared.

Agricultural drainage water (ADW) reuse is the most promising option to increase the availability of water for irrigation. The pollution of drainage networks and the Nile River water supply shortage threaten the largest ADW reuse project in Egypt (El-Salam Canal), especially following the construction of the Grand Ethiopian Renaissance Dam (GERD). Accordingly, a one-dimensional hydrodynamic and water quality (WQ) simulation model was built as a tool to manage the quantity and quality of the canal water using MIKE 11 modules. Three proposed scenarios aimed to assess the current situation (Scenario 1), the best WQ parameter reduction ratio of the highly pollutant drains (Scenario 2), and the effect of the construction of the GERD on the canal WQ (Scenario 3). The results provided a quantitative canal WQ management tool to comply with the standards for irrigation purposes and illustrated that after the construction of the GERD, the WQ of the canal will worsen, especially in the summer season. As such, the treatment of the water in the El-Serw and Bahr Hadous drains before mixing with the El-Salam Canal is considered the best option to protect the WQ of the canal from deterioration.