4. Conclusions

In volcanic mountain watersheds, the groundwater system can play an active role in hydrological processes. The groundwater system at the headwater of the

### Andean Mountain Groundwater, Drinking Water Sources, and Vulnerability: A Case Study… DOI: http://dx.doi.org/10.5772/intechopen.85016

Diguillín River is very active and, at least, has two main subsystems: the existent aquifers located at the volcanic complex itself and the fractured system of the Renegado watershed. Those groundwater systems produce almost all the streamflow of the river at the end of the Chilean summer and early fall.

Each volcano that exists in Chile is a complex aquifer system by itself. There is a lack of knowledge about the groundwater system at the volcanic complexes. The structure of the aquifer systems and the recharge and discharge processes are unknown. Advances in understanding of those processes will allow advantage to be taken from the geothermal potential of the volcanic complexes.

This analysis makes evident the reasons why the Diguillín River has stable minimum flows during the dry season and why the Renegado Creek has a lower specific streamflow. However, those differences were not so obvious 3 years ago, at the start of this research. It is important to emphasize that in practical engineering, the supposition of constant specific streamflow between neighboring watersheds is widely used. Thus, it is important to carefully check this hydrological similarity through an analysis of the climatic and geomorphologic characteristics, soil type, and use. But in watersheds influenced by volcanic systems, it will be necessary to carefully analyze the geological conditions, especially in relation to fractured rock systems.

The highly permeable soil and the fractured rock system in the Renegado subwatershed, where there is significant tourism development and construction of weekend houses, raise questions about the fate of pollutants introduced to the systems by wastewater infiltration from septic tanks. The pathways between pollutant recharge areas and spring discharge are unknown and must be identified and ideally measured in order to improve the sustainable development of the watershed.
