3. Results and discussion

#### 3.1 A plausible explanation for the groundwater connection

As hydrological processes should be highly connected with the geological features in fractured rock settings, it is important to give a look into local geological and lithological conditions in order to have a wider insight into the system under study.

The geology of the upper section of the Diguillín watershed is strongly influenced by the volcanic processes associated with the Nevados del Chillán volcanic complex [15, 16]. This volcanic complex is composed of several types of structures created by different processes that have occurred for approximately 650,000 years [15].

The Nevados del Chillán volcanic complex possesses cold and hot springs distributed along its edge [15], from which it may be inferred that the volcanic complex behaves in a form similar to the systems described by [6, 7]. The existence of cold and hot springs indicates the existence of at least two aquifers: a superficial one that receives its recharge by infiltration of rainwater and snowmelt discharging in cold springs and a deeper system, which is recharged from the superficial system and is in contact with the magma chamber, heating the water and producing vapor that feeds the thermal springs (Figure 5a).

As well as the thermal springs around the volcanic complex, there is a large cluster of hot and cold springs in the "Valle de Aguas Calientes" (Hot spring valley)
