Author(s): Ivan Portoghese; Vincenzo Totaro; Claudia Panciera; Vito Iacobellis

Linked Author(s): Ivan Portoghese, Claudia Panciera, Vito Iacobellis

Keywords: Water balance modeling; Climate chenge impact; Ungauged basins; Semi-arid hydrology

Abstract: Despite the simplified representation of basic hydrological processes, large-scale hydrological models are increasingly adopted for studying catchment water balance and developing water resources scenarios under changing climate conditions. In this work, we exploited the results of the BIGBANG model developed for the entire Italian territory (Braca et al., 2021) with a spatial resolution of 1x1 km and monthly time-scale. We considered its application in an ungauged semi-arid basin of Puglia (Southern Italy) by comparison with output of a distributed model (Giordano et al., 2003), validated at regional level and suitable for representing both the surface and sub-surface water balance at daily scale. This exercise was carried out in the Canale Reale river basin, flowing for about 50 km and reaching the coastal wetlands of Torre Guaceto along the Adriatic, one of the most important nature reserve in Italy (SCI IT9140005; SPZ IT9140008). As happened in most of the Puglia region, the agricultural intensification in the last 50 years caused a progressive increase in groundwater withdrawals, also given the lack of surface water resources. Groundwater withdrawals have caused imbalance between inflows and outflows, highlighted by expanding phenomena of saline contamination affecting both the wetland and the surrounding aquifer system. From the hydrogeological viewpoint, this catchment is characterized by two locally overlapping aquifers, of which the top one interacts with the hydrographic network, draining the aquifer in the wettest periods and feeding it in the dry periods. While, the bottom aquifer is hosted in the fractured limestones below the sandy-silty deposits. The massive groundwater exploitation is probably responsible for the transformation of the runoff regime from permanent to seasonal during the past decades and became a potential threat to the wetland conservation in the coming future. Dealing with the application of BIGBANG monthly model in ungauged basins, we started from the calibration of the daily rainfall-runoff model through the use of semi-quantitative information related to past flood events, acquired from newspaper reports, and seasonality of hydrological regime based on local knowledge. Among the calibrated parameters for the daily model, recession time of sub-surface reservoirs, together with storage capacity, were the most relevant for the likely reconstruction of hydrologic response in terms of simulated daily streamflow. Besides the monthly sum-up of daily flowrates, the comparison with the BIGBANG output, allowed to investigate dynamics in the groundwater basin area in representing the baseflow component of the simulated streamflow, based on the known conceptual model of the hydrogeological setting. This example application proved the effectiveness of the proposed approach for the exploitation of large-scale models in ungauged semi-arid basins.

DOI: https://doi.org/10.3850/IAHR-39WC2521711920221812

Year: 2022