The Tempisque-Bebedero catchment system is located in the north-western Guanacaste province of Costa Rica close to the border to Nicaragua. The total size of the system is around 5460km2 due to the two catchments (Tempisque and Bebedero) that share the same estuary at Palo Verde National Park and are also hydraulically connected via water transfers. Therefore, the rivers Tempisque and Bebedero with their respective catchments were defined as a single catchment system (Figure 1). The catchment forms part of the Central American dry corridor and is vulnerable to droughts. It was recently assigned a national priority by the Costa Rican authorities.