“Water for All: A study that shows which watersheds we must protect today to live tomorrow”

Galápagos is a living laboratory where every environmental decision matters. On Santa Cruz, the most populated island of the archipelago, freshwater is a limited and increasingly vulnerable resource due to urban growth, agricultural pressure, saltwater intrusion, and climate change. In this context, understanding how water behaves across the landscape becomes essential for water security.

Our study proposes a geomorphological approach to identify which watersheds offer the best conditions for water conservation, which require immediate intervention due to their susceptibility to erosion, and which could be suitable for sustainable agricultural activities.

¿Why Study the Shape of the Terrain?

Watersheds act as natural “funnels” that capture, channel, and store rainfall. Their shape (whether long, round, steep, or flat) directly influences runoff velocity, infiltration capacity, and erosion risk.

For this study, 24 watersheds on Santa Cruz were analyzed using 18 morphometric parameters derived from 4.7 m digital elevation models corrected with official topographic data from the Charles Darwin Foundation. The evaluated parameters include:

• Drainage density, indicating how dissected the terrain is.
• Relief and roughness, reflecting the topographic energy.
• Watershed shape, useful for estimating how quickly flow becomes concentrated.
• Stream frequency, which indicates the complexity of the drainage network.

These variables were integrated into a composite index that allowed us to rank the watersheds according to their susceptibility to erosive processes and their water retention potential.

¿Which watersheds are priorities for conservation and which for sustainable use?

The results show clear contrasts. Watersheds SW7, SW5, and SW24 have the lowest values in the composite index, indicating high vulnerability due to steep slopes, high drainage density, and greater erosive energy. These areas require urgent measures such as reforestation, small check dams, runoff management, and soil protection.

On the other hand, watersheds such as SW15, SW22, SW19, and SW1 fall under the low-priority category, not meaning neglect, but rather greater geomorphological stability. These areas show higher water retention capacity, lower erosivity, and therefore greater potential for sustainable agriculture and water harvesting.

In a territory where 97% of the surface is under conservation, this type of tool helps guide decisions without compromising the ecological integrity of the Galápagos National Park. It also distinguishes areas that require immediate intervention from areas suitable for implementing infiltration, harvesting, or storage systems.

A method applicable to other volcanic islands

The value of this work extends beyond Santa Cruz. The methodology can be replicated on other volcanic islands worldwide, where water scarcity, young soils, and human pressure create similar challenges. Moreover, geomorphological prioritization can be integrated into hydrological models, risk analyses, land-use planning, and resilient agricultural strategies.

Conclusion

This study proposes a detailed and accessible watershed-morphometry framework to improve decision-making in island territories. Identifying both critical watersheds and areas suitable for agriculture enhances preventive management and strengthens water security. In an archipelago as sensitive as Galápagos, understanding the shape of the terrain becomes a powerful tool to safeguard water, support local production, and adapt to climate change.