Jorge Gironás

A stochastic model of streamflow for urbanized basins

Given the critical role of the streamflow regime for instream, riparian, and floodplain ecosystem sustainability, modeling the long-term effect of urbanization on streamflow is important to predict possible changes in stream ecosystems. Since flow duration curves are largely used to characterize the streamflow regime and define indices for stream ecosystem health, we present two stochastic models, with different levels of complexity, that link the key physical features of urbanized basins with rainfall variability to determine the resulting flow duration curves. The two models are tested against 11 basins with various degrees of urban development, characterized by the percentage of impervious areas in the basin. Results show that the more complex model needs to be used to reproduce accurately the entire flow duration curve. The analysis performed suggests that the transformation of green (i.e., water used in evapotranspiration) to blue (i.e., streamflow) water in urbanized basins is an important long-term source of ecohydrological alteration. The modeling scheme also provides useful links between rainfall variability, urbanization levels, and some streamflow indices of high and low flows.

Exploring possible connections between hydrological extreme events and climate change in central south Chile

Abstract Motivated by recent extreme flow events in the Mataquito River located in the Mediterranean region of Chile, we performed a detailed trend analysis of critical hydroclimatic variables based on observed daily flow, precipitation and temperature within the basin. For the period 1976–2008, positive trends in temperature were observed, especially during spring and summer months. At the same time, we found negative trends in the frequency and intensity of precipitation, especially during spring months. We observed an increasing difference between average streamflow in the rainy season as compared to the snowmelt season. Part of this trend is caused by larger flows during autumn months, although no positive precipitation trends are observed for these months. Finally, significant reductions in minimum flow during spring/summer and a disproportionate concentration of high-flow events occurring in the last 10 years were also identified. These high-flow events tend to happen during autumn months, and are associated with high precipitation and high minimum temperatures. Based on a simple assessment of changes in irrigated agriculture and land use, we concluded that other non-climatic factors seem not to be as relevant to the detected flow trends. All these results are in accord with future climate change scenarios that show an increase in temperature, a reduction in average precipitation and a reduction in snow accumulation. Such future scenarios could seriously hamper the development of economic activities in this basin, exemplifying also a fate that may be shared by other similar basins in Chile and in other regions of the world. Editor Z.W. Kundzewicz Citation Vicuña, S., Gironás, J., Meza, F.J., Cruzat, M.L., Jelinek, M., Bustos, E., Poblete, D., and Bambach, N., 2013. Exploring possible connections between hydrological extreme events and climate change in central south Chile. Hydrological Sciences Journal, 58 (8), 1598–1619.

A model for simulating the performance and irrigation of green stormwater facilities at residential scales in semiarid and Mediterranean regions

Abstract Impervious areas change hydrological processes, reducing infiltration and evapotranspiration, and increasing direct runoff. Stormwater practices using green infrastructure are implemented locally to control runoff and preserve the hydrological cycle. Applying these techniques in semiarid and Mediterranean regions requires accounting for aspects related to the maintenance of green areas. This study develops the Integrated Hydrological Model at Residential Scale, a continuous model for representing the performance and irrigation of green stormwater facilities at residential scales. Among other relevant process, the model simulates evaporation from bare soil and redistribution between soil layers. Different components of the model were tested using laboratory and numerical experiments, and then an application to a case study and a sensitivity analysis were carried out. The model identifies significant differences in the performance of a rain garden with different vegetation, climate and irrigation practices and provides good insight for the maintenance needs of green infrastructure for runoff control.

Using a Statistical Preanalysis Approach as an Ensemble Technique for the Unbiased Mapping of GCM Changes to Local Stations

AbstractAccounting for climate change, GCM-based projections and their uncertainty are relevant to study potential impacts on hydrological regimes as well as to analyze, operate, and design water i...

River Mouths and Coastal Lagoons in Central Chile

River mouths and coastal lagoons in central Chile are some of the most dynamic ecosystems in the country. They are controlled by a great variety of natural and anthropic factors, which have confer these ecosystems a high environmental and human value. The diversity of these ecosystems is mainly due to a complex set of parameters that define them: from the hydrological and climatic variability, the heterogeneity of the river mouths, the high energy of the coasts, to different annual sediment availability, etc. These parameters, as well as meteorological and hydro-morphodynamics, all create a very unique combination, even at a global scale, being similar only to some sectors of South Africa, Australia and New Zealand.