So-called “Type IX” chute spillways with impact baffle blocks have been used successfully around the globe for over 50 years. A key advantage of the chute spillway is the elimination of a costly stilling basin allowing for a more simplistic outlet works design. The current design process is based upon physical models developed in the 1950s and observation of completed projects over the last 50 years. The design procedure is empirical and provides the designer with a range of workable layouts, baffle heights, and baffle spacing. Unfortunately, this approach may not be optimal. This first study of a longer research effort focus uses Monte-Carlo simulations and computational fluid dynamics (CFD) to examine the design methodology and physical model basis for the current design procedure. Initially, the study examined the design procedure with a Monte-Carlo simulation to explore the range of acceptable designs that can be realized. Then, using CFD, full-scale prototype (located in Gila, Arizona USA) physical model result that were a key basis for the current design procedure were recreated. The study revealed that a wide range of acceptable chute designs can result from following the current design procedure but that some of these may be better than others. The study also outlines future research efforts needed to revise the current design methodology.

Adequate design of energy dissipation structures is essential for effective flood control. Theoretical analysis of these structures is complex due to the turbulent nature of supercritical flow and is further complicated by air entrainment. The effect of aeration on water flow has been one of most analysed phenomena during the last decades due to its influence on the behaviour of hydraulic structures. The objective of this study is to characterize the influence of aeration on the boundary friction in supercritical conditions and fully turbulent flows. Our analysis is based on a physical model designed to reproduce these phenomena in the Hydraulics Laboratory of CEDEX (Spain), funded by a research project of the Spanish Ministry of Economy.

The structure consists of a spillway chute 6.5 m high, 0.5 m wide and slope of 75%, followed by a 10 m horizontal channel where the hydraulic jump is confined. Water and air are supplied by a pump and compressors and controlled at the entrance by several valves and flowmeters. This device has a pressurized intake, with 10 m head of additional pressure, which generates the mixture to reproduce different scenarios of emulsified flow, with rates up to 300 l/s of water and 3000 l/min of air. Under these conditions, velocity ranges from 6 to 12 m/s with Froude number between 4 and 11.

Currently, the channel is monitored to measure the velocity profile and air concentration in the flow. The aim of our research is to analyse the relation between air concentration and energy dissipation by friction, in order to link the air concentration rate to the Manning roughness number and other methods of friction quantification. This characterization is based on the velocity and concentration profiles along the vertical axis. We collected data of 12 different scenarios to analyse the relationship between aeration rate and roughness coefficient. We found that greater air entrainment implies acceleration of the flow. Since friction is the main energy dissipation mechanism in the chute, hydraulic structures should be designed to minimize air entrainment and thus enhance energy dissipation by friction.

As the alteration of the precipitation regime due to climate change, extreme precipitation events causing floods with the negative impacts on urban water infrastructure are observed today and expected to be observed in the future. This study examines the potential impacts of climate change and investigates the impact of these changes into urban stormwater network design. Rainfall analysis with stationary and nonstationary approach for observed and future conditions is performed for the (1950-2015 period) observed data of 5, 10, 15, 30 minutes and 1, 2, 3, 6 hour and projections (2015-2098 period) of 10, 15 minutes and 1, 6 hour for Ankara province, Turkey. Daily projections are disaggregated to finer scales, 5 minutes storm durations, then five minutes time series aggregated to the storm durations that are subject of interest and used for future period. Nonstationary Generalized Extreme Value (GEV) models and stationary GEV models for observed and future data are obtained. Nonstationary model results are in general exhibited smaller return level values with respect to stationary model results of each storm duration for the observed data driven model results. Considering the projected data driven model results; on average nonstationary models produce mostly lower return levels for mid and longer return periods for all storm durations and return periods except one hour storm duration. Depending on the models and Representative Concentration Pathways (RCP), there are different results for the future extreme rainfall input; yet all results indicate a decreasing extreme trend. The magnitude of future period extreme rainfall decreases with respect to observations. Return periods of the extreme rainfall increase in the future period therefore, not considering these trends may lead to overdesign of the stormwater network.

A significant spatio-temporal alteration of traditional patterns for hydrological components´ behavior is currently being observed. In this sense, a higher variability, more frequent and unpredictable extreme events (rainfall, flood and drought) occur in many areas. This is primarily due to global warming, which is producing a growing variability and uncertainty of water systems and specially, rivers´ runoff. The understanding of these modifications and, consequently, this adaptive rivers´ behavior is not trivial and requires new approaches incorporating dynamic and stochastic approaches. Causal Reasoning, supported by Bayesian modelling is a powerful stochastic approach to extract the time dependent logical structure that inherently underlies hydrological series. The river basin memory is dynamically and stochastically characterized in terms of the runoff dependence strength over the time. In this study, by means of causality, the Temporally Conditioned/Non-conditioned runoff (TCR/TNCR) fractions are identified and quantified. This research has important implications and applications, such as to the knowledge of the historical adaptive rivers´ behavior, or to reservoirs´ dimensioning optimization. This approach has been successfully applied to an unregulated river basin in Spain with a very high dependence temporal runoff behavior, within Júcar river basin (Mijares). Having a tool that could dynamically adjust the reservoir and/or channel capacity may help for reaching the optimal design and dimensioning of hydraulic infrastructures, which involves a lot of economic savings. Further work will largely comprise the introduction of the spatial dimension so the tool can integrated a full spatio-temporal analysis. Furthermore, the analyzed runoff behavior trends will be further used for building predictive models.

We evaluate alternatives for the management of water for agriculture under climate change in six representative basins of Southern Europe: Duero-Douro, Ebro, Guadalquivir, Po, Maritsa-Evros and Struma. Management objective is maximizing water availability, understood as the maximum demand that can be satisfied with a given reliability. We focus on water availability for agriculture. For simplification we are assuming only two types of demands: urban and irrigation. Water is first allocated to urban demands following the established priority and the remaining resources are allocated to agriculture. If water availability is not enough to satisfy all irrigation demands, management measures are applied with the goal of achieving a balance between resources and demands. We present an analysis of three possible management measures to face water scarcity in the long term scenario: increasing reservoir storage, improving efficiency of urban water use and modifying water allocation to environmental flows. These management measures are globally evaluated for the selected basins in three representative climate scenarios, comparing their possible range and effectiveness. While in some basins, like Ebro or Struma, measures can significantly increase water availability and compensate for a fraction of water scarcity due to climate change, in other basins, like Guadalquivir, water availability cannot be enhanced with management measures and irrigation water use will have to be reduced.