Dr. Muñoz-Ortiz, Enrique

Groundwater storage and discharge are important processes that have not yet been sufficiently studied in some parts of Chile. Additionally, in watersheds without snow cover or glaciers, groundwater storage and release are the main sources of minimum flow generation; therefore, improvements are required to characterize this process. This study aimed to use recession flow analysis to link groundwater storage depletion to the predominant geological characteristics of each watershed in order to improve our understanding of the groundwater storage-release process in 24 watersheds in south-central Chile. The results allowed different groundwater storage behaviors associated with different geological characteristics to be identified, making recession flow analysis a valuable tool for improving the representation and conceptualization of this process in order to advance toward better minimum flow predictions.

Due to population growth and expansion in the agricultural and industrial sectors, the demand for water has increased. However, water availability in some regions has decreased due to climate change trends and variability, necessitating innovative strategies and adaptation in water allocation to avoid conflicts among users in a hydrological system. This paper presents a resilience analysis and a conceptual hydrological modeling approach to evaluate the resilience capacity of a new water allocation rule in the Laja Lake basin in southern Chile. Resilience assessments included absorptive and adaptive capacities with four system states: resilient, susceptible, resistant, and vulnerable. A modeling approach was used considering the climate variability uncertainty and climate change trends of the Laja system. Characterization of adaptive and absorptive capacities showed that the Laja Lake basin moved from resistant to vulnerable. Hydrological modeling analyses showed that after a new water allocation agreement, the Laja Lake system is moving from vulnerable to susceptible, since the new rule has more adaptive alternatives to face climate variability. The new rule diminishes the possibilities of conflicts among users, ensuring the fulfillment of water needs for uses such as farming and ecosystem services such as landscaping, and allows for increased water allocation for energy in wet hydrological years.

Choosing a model that suitably represents the characteristics of a watershed to simulate low flows is crucial, especially in watersheds whose main source of baseflow generation depends on groundwater storage and release. The goal of this investigation is to study the performance and representativeness of storage-release process modeling, considering aspects such as the topography and geology of the modeled watershed through regional sensitivity analysis, in order to improve low-flow prediction. To this end, four groundwater storage-release structures in various watersheds with different geological (fractured and sedimentary rock) and topographic domains (steep and gentle slopes) were analyzed. The results suggest that the two-reservoir structure with three runoff responses is suitable (better) for simulating low flows in watersheds with fractured geological characteristics and rugged or steep topography. The results also indicate that a one-reservoir model can be adequate for predicting low flows in watersheds with a sedimentary influence or flat topography.

The hydrology of scarce-data areas, such as the mountainous area of the Andes, is poorly known mainly owing to the lack of data. Global gridded climatological datasets (GGCDs) are becoming more precise and common, but the utility of these datasets and their applicability to complex hydrological systems are still not yet well determined. In this paper the reliability of a GGCD is evaluated as an alternative source to supply the lacking in situ observations, with the aim of studying the hydrology of a mountainous area in south-central Chile. The GGCDs are found to recover the climate variability in Andean areas, and partially recover the orographic effect caused by the mountains. A finding of practical relevance is that GGCDs could be considered as an adequate source for performing hydrological models and studies under high spatial variability and scarce-data environments such as the Andes.

Different sets of parameters and conceptualizations of a basin can give equally good results in terms of predefined objective functions. Therefore, a need exists to tackle equifinality and quantify the uncertainty bands of a model. In this paper we use the concepts of equifinality, identifiability and uncertainty to propose a simple method aimed at constraining the equifinal parameters and reducing the uncertainty bands of model outputs, and obtaining physically possible and reasonable models. Additionally, the uncertainty of equifinal solutions is quantified to estimate the amount by which output uncertainty can be reduced by knowing how to discard most of the equifinal solutions of a model. As a study case, a conceptual model of the Chillán basin in Chile is carried out. From the study it is concluded that using identifiability analysis makes it possible to constrain equifinal solutions with reduced uncertainty and realistic models, resulting in a framework that can be recommended to practitioners, especially due to the simplicity of the method.