Integrated ecological modelling for evidence-based determination of water management interventions in urbanized river basins: Case study in the Cuenca River basin (Ecuador) (original) (raw)
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MODELING ACEQUIA WATER USE IN THE RIO HONDO WATERSHED
Acequias are canals that channel water from higher to lower elevation to be used for flood irrigation of agricultural fields, which can result in the phenomenon of recharging local aquifers. In this study, a computer model was constructed to quantify the effects of agricultural water use in the Rio Hondo watershed, north of Taos, New Mexico. The watershed is home to 13 regional acequias, which flow through three separate communities. The Rio Hondo simulation aggregates water use in all 13 acequias to provide a general characterization of the impact of flood irrigation on the local aquifer. The simulation is constructed in STELLA 9.1, a generalized system dynamics modeling platform that uses stocks, flows, and converters to map out interrelated components of any system. The Rio Hondo simulation models surface and groundwater availability, crop productivity, and crop market value across five climate change scenarios, five crop distributions, and three irrigation methods. The model is based on publically available data and a range of assumptions. The simulation was constructed to display dynamic trends that occur between surface and groundwater flows and show how these trends may respond to changes in crop distribution, irrigation practices and stream flow within the watershed. The simulation does not purport to project actual values for surface and groundwater yields across these scenarios. Based on an estimated hypothetical volume, the local aquifer stabilizes under flood irrigation, while its volume diminishes by as much as 20% under drip irrigation. Surface water flows in the Rio Hondo are projected highest to lowest in the drip irrigation scenario where water saved from drip was returned to the river, then the flood irrigation scenario where no water savings took place, and finally the drip scenario where water savings from drip were re-allocated for agricultural use. Again, these projections are not meant to represent hard and fixed predictions of future water availability or crop productivity within the watershed. Rather, they are meant to highlight how various components of this manmade-natural system may respond to future changes, with the ultimate goal of engaging a broad range of stakeholders in envisioning alternative management strategies for future water use within the watershed.
"European river basin authorities are responsible for the implementation of the new river basin management plans in accordance with the European Water Framework Directive. This paper presents a new methodology framework and approach to define and evaluate environmental flow regimes in the realistic complexities that exist with multiple water resource needs at a basin scale. This approach links river basin simulation models and habitat time series analysis to generate ranges of environmental flows (e-flows), which are evaluated by using habitat, hydropower production and reliability of water supply criteria to produce best possible alternatives. With the use of these tools, the effects of the proposed e-flows have been assessed to help in the consultation process. The possible effects analysed are impacts on water supply reliability, hydropower production and aquatic habitat. After public agreements, a heuristic optimization process was applied to maximize e-flows and habitat indicators, while maintaining a legal level of reliability for water resource demands. The final optimal e-flows were considered for the river basin management plans of the Duero river basin. This paper demonstrates the importance of considering quantitative hydrologic and ecological aspects of e-flows at the basin scale in addressing complex water resource systems. This approach merges standard methods such as physical habitat simulations and time series analyses for evaluating alternatives, with recent methods to simulate and optimize water management alternatives in river networks. It can be integrated with or used to complement other frameworks for e-flow assessments such as the In-stream Flow Incremental Methodology and Ecological Limits of Hydrologic Alteration."
Multidisciplinary models are useful for integrating different disciplines when addressing water planning and management problems. We combine water resources management, water quality and habitat analysis tools that were developed with the Decision Support System AQUATOOL at a basin scale. The water management model solves the allocation problem through network flow optimisation and considers the environmental flows in some river stretches. Once volumes and flows are estimated, the water quality model is applied. Furthermore, the flows are evaluated from an ecological perspective by using time series of aquatic species habitat indicators. This approach was applied in the Tormes River Water System, where agricultural demands jeopardise the environmental needs of the river ecosystem. Additionally, water quality problems in the lower part of the river result from wastewater loading and agricultural pollution. Our methodological framework can be used to define water management rules that maintain water supply, aquatic ecosystem and water quality legal standards. The integration of ecological and water management criteria in a software platform with objective criteria and heuristic optimisation procedures allows for the realistic assessment and application of environmental flows. Here, we improve the general methodological framework by implementing a hydrological alteration assessment of e-flow regime scenarios.