Hydrogeological assessment of springs and groundwater in Carrizal, Costa Rica

Abstract: The main purpose of this thesis is to increase the understanding of how hydrogeological conditions are affecting the local water resources in Carrizal on the Barva Volcano, Costa Rica. Hydrogeological investigations of spring characteristics, soil infiltration rates and water flow in springs and rivers were conducted at the study area in Costa Rica as part of a Minor Field Study (MFS). A statistical analysis comparing spring flow rates and precipitation, based on data collected by Costa Rican organisations during several years, led to the conclusion of a potential water age of 0-24 months in aquifers discharging in the assessed springs. A recent decrease of flowrate in the local springs on the volcano can therefore be explained by less precipitation than the average in the years 2018 and 2019. Spatial and temporal variabilities in spring flow, change in groundwater storage (ΔS) and precipitation patterns were analysed to determine groundwater flow systems communicating with springs in the study area. However, specific groundwater recharge areas were hard to delimit since possibly multiple flow systems were found to be communicating with the same spring. Overall high values of ΔS were calculated from the water balances but more research is needed to see if this contributes to Mountain Block Recharge (MBR) or discharges in unstudied areas further down on the volcano.