22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Response of spring discharge to climate changes in hard rock aquifers of different lithologies

24 Sep 2019, 11:15
15m
Conference room 2.2 ()

Conference room 2.2

Oral Topic 2 - Groundwater and climate change Parallel

Speaker

Dr Maria Filippini (University of Bologna)

Description

Hard rock aquifers, either sedimentary (turbidites and arenites) or igneous (ophiolites), dominate the landscape of the northern Apennines (Italy), in a climatic framework midway between sub-tropical mediterranean and mountainous humid. The main rainfall events occur in autumn and spring, providing an average annual precipitation between 1000 and 3000 mm/y. On the northern slope of the Apenninic chain an increased interannual variability in precipitation and temperature regime was observed in recent years with extreme droughts (e.g. in years 2012 and 2017) alternated to more rainy years, e.g. 2014 and 2018 when extreme rainfall events were concentrated over short time periods. The effects of these recharge pattern modifications on spring discharge are still mostly unknown. Exploiting the available rainfall, snowfall, air temperature and spring discharge data from the monitoring network of Emilia-Romagna region, an analysis was carried out to assess the relationship between direct aquifer recharge and the discharge of springs on a hydrologic year time scale. Discharge was monitored on 77 springs draining 44 aquifer bodies pertaining to 7 different lithologies. The relationship between recharge and discharge was determined for 3 hydrologic years that were selected based availability of monitoring data (i.e. 2010-2011, 2013-2014, 2016-2017). The 62% of the investigated aquifer bodies showed a positive correlation between aquifer recharge and spring discharge. The 19% of aquifers didn’t show a clear recharge-discharge relationship whereas the remaining 19% showed a negative correlation. Positive correlations dominate in aquifers with large recharge areas located at high elevation and characterized by extended woodland cover. From a lithologic viewpoint, the aquifers showing the most positive correlation were calcareous turbidites and arenites followed by siliciclastic turbidites. Ophiolites and fewer outcrops of dolomites and limestones did show a neutral to negative trend. The occurrence of such negative trends may be related to increased runoff due to extreme rainfall events (i.e. more than 30 mm/h) over less forested and steeper recharge areas. The overall high percent of positive trends observed between direct recharge and average spring discharge proves that changes in rainfall regime are likely to cause significant effects on spring discharges even in the short term (i.e. over a year time scale). Moreover, the modification of rainfall patterns observed in the northern Apennines (e.g. increased rainfall compared to snowfall, lower on ground permanence of snow cover, increased occurrence of extreme rainfall events) are likely to cause significant decrease of direct recharge and thus a decrease of spring discharge. The significant interannual variability of rainfall occurred in the last years provided a good platform to evaluate the effects of climate change on aquifer recharge and spring discharge. The results may be used as well to evaluate the effects of future climate changes forecasted via emissions scenarios and global circulation models.

Primary authors

Dr Maria Filippini (University of Bologna) Dr Stefano Segadelli (Geological, Seismic and Soil Service, Emilia-Romagna Region Administration, Bologna) Alessandro Gargini (University of Bologna)

Presentation Materials

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