Slope stabilization through groundwater management with limited hydrogeological data: a case study from Majes, southern Peru

Water table rise near a cliff may trigger a landslide due to the associated increase pore pressure and decrease in frictional resistance. One main cause of water table rise is intense irrigation for agriculture in arid and semi-arid regions. One such case is in Majes, southern Peru, where a landslide has evolved near an intensively irrigated agricultural area. Mitigation strategies for landslides exist, such as physical strengthening of the cliff, but can be expensive. We describe a groundwater management approach to reduce the pore pressure in the vicinity of the cliff to either slow the propagation of an existing landslide or prevent the initiation of a new landslide. A 3D numerical groundwater flow model was built for the Majes area which employs the limited data existing on the local hydrogeology. Simulations were run to understand the connection between the hydraulic properties and the water table level change due to irrigation and pumping. Results show that through a series of pumping wells near the cliff edge, the pore pressure can be decreased effectively. Moreover, decreasing the water table via pumping can be accomplished in 25–35% of the time it took to elevate the water table level by irrigation. In addition, the pumping can capture water that could be reused for irrigation. Thus, based on our analysis, we conclude that wells could provide a groundwater management approach that keeps the pore pressure at low levels to mitigate landslide processes and simultaneously supplies water for irrigation existing and future irrigation-heavy agriculture in semi-arid environments.