Understanding land cover influence on water resources in south-central Chile: A hydrological modelling with baseflow recession analysis approach

Land cover change and its effect on water resources has been a continuous concern in south-central Chile. In this regard, we use two methodologies to study the effect of different land covers on the hydrological processes in several experimental catchments (<100km²) located between 36°S to 39°S. These experimental catchments include native forest and commercial plantations (Monterrey Pine and Eucalyptus) land covers. The first methodology is the use of hydrological modelling to analyze the land cover influence on the water yield of a catchment. [1] compared hydrological and evapotranspiration models and selected the best which represented daily stream flow. The best results were obtained through the more complex model (i.e GR6J and Oudin PET model) which can account for groundwater interaction. The second methodology is the use of the recession coefficient (a) as a metric for baseflow recession analysis, which is a good index of the risk of flow decreasing below a threshold. This coefficient represents the rate of decrease in streamflow after a rainfall event. [2] investigated through mathematical modelling how (a) differs between land cover within the same study sites as [1] study mentioned above. This coefficient did not differ in winter, indicating a similar soil saturation, but some differences were found in summer.  It was determined that (a) was similar between land cover types. Considering both methodological approaches we can conclude that at the experimental catchment scale geology and the fractured rock system play a crucial role in surface-groundwater interactions in these ecosystems. Therefore, future investigations should be focused on subsoil processes and surface-groundwater interaction. Due to its Mediterranean climate, rainfall in Chile is concentrated during winter months, when trees are dormant, meaning that they do not significantly transpire, and a larger proportion of rainfall can infiltrate into the soil. Therefore, metrics such as (a) can help develop landscape planning strategies to increase water availability in conjunction with hydrological modelling. 

References:

[1] Flores, N., Rodríguez, R., Yépez, S., Osores, V., Rau, P., Rivera, D., & Balocchi, F. (2021). Comparison of Three Daily Rainfall-Runoff Hydrological Models Using Four Evapotranspiration Models in Four Small Forested Watersheds with Different Land Cover in South-Central Chile. Water, 13(22), 3191.

[2] Balocchi, F., Flores, N., Arumí, J. L., Iroumé, A., White, D. A., Silberstein, R. P., & Ramírez de Arellano, P. (2021a). Comparison of streamflow recession between plantations and native forests in small catchments in Central‐Southern Chile. Hydrological Processes, 35(6), e14182.