Hydrologic Analysis of an Intensively Irrigated Area in Southern Peru Using a Crop-Field Scale Framework

Abstract

Majes is one of the largest agricultural areas in the Arequipa region (southern Peru). Low seasonal precipitation and increasing water demands for agricultural irrigation, industry, and human consumption have made water supply projections a major concern. Agricultural development is becoming more extensive in this dry, sunny climate where crops can be grown year-round. However, because this type of project usually involves significant perturbations to the regional water cycle, understanding the effects of irrigation on local hydrology is crucial. Based on the watershed-scale Soil and Water Assessment Tool (SWAT), this investigation focuses on the impacts of intensive irrigation on hydrological responses in the Majes region. This study is unique because we allow for crop-field scale input within our regional-scale model to provide information at this smaller scale, which is important to inform local stakeholders and decision makers. Each hydrologic response unit (HRU) was generated to represent an individual crop field, so that management practices could be applied according to real-world scenarios. The management file of each HRU was modified to include different operation schedules for crop rotation, irrigation, harvest, and tillage. The model was calibrated and validated against monthly observed stream discharge during the 2009–2020 period. Additionally, evapotranspiration, irrigation water volume, and daily stream discharge downstream of the local river (Siguas) were used to verify the model performance. A total of 49 sub-basins and 4222 HRUs were created, with 3000 HRUs designated to represent individual crop fields. The simulation results revealed that infiltration from agricultural activities in Majes represents the majority of annual groundwater return flow, which makes a substantial contribution to streamflow downstream of the Siguas River. Simulations also suggested that groundwater flow processes and the interactions between surface and groundwater have a major impact on the water balance of the study area. Additionally, climate variability had a higher impact on surface runoff than on groundwater return flow, illustrating that the groundwater component in the study area is important for future water resources resiliency under expected climate change scenarios. Finally, there is a need to perform a follow-up implementation to provide a guideline for decision-makers to assess future sustainable water resources management under varying climatic conditions for this arid irrigated system.

Water Resources Evaluation and Sustainability Considering Climate Change and Future Anthropic Demands in the Arequipa Region of Southern Peru

“…Irrigation efficiency is defined as the amount of water used by crops, compared to total water applied through irrigation (e.g., [41]). The highest irrigation efficiency reported in the five watersheds is 0.77 for the sprinkling irrigation system of Majes [16]. However, the dominant irrigation in the five watersheds is traditional gravity (flooding) methods, which have lower efficiencies (e.g., [42]).…”

“…Similarly, the United States Agency for International Development (USAID) [15] applied a Water Evaluation and Planning System (WEAP) model to the Quilca watershed, including most of the individual water uses and "naturalizing" all of the reservoirs in the area. Also, in the Quilca watershed, Wei et al [16] developed a SWAT model to assess the connection between intensive irrigation and groundwater return flows to an adjacent river in the Majes district, concluding that most of the applied irrigated water is lost through percolation, while Daneshvar et al [17] applied a SWAT model in the El Frayle reservoir (Quilca watershed) using the streamflow naturalization approach. However, while water consumption in the Arequipa Region continues to increase, the combined effects of both climate change and human activities on water resources availability is currently unknown.…”

High-Temporal-Resolution Rock Slope Monitoring Using Terrestrial Structure-from-Motion Photogrammetry in an Application with Spatial Resolution Limitations

“…Landslides are a common occurrence in the river valley, with most activity occurri on the northern valley wall [19]. There are a few publications related to landslides in th valley and neighboring valleys that have investigated groundwater conditions [19,20], a alyzed geophysical survey data [21], monitored landslide activity with satellite remo sensing and GPS [22,23], and conducted detailed investigations of existing landslides [2 All of these publications point to increased groundwater levels due to irrigation as a maj contributing factor to landslide activity. Similar relationships between landslide activi and irrigation can be seen in several other regions globally [25].…”

Seismic Characterization of a Landslide Complex: A Case History from Majes, Peru

“…The Majes I region is situated 60 km west of the regional capital Arequipa in an arid, high-altitude desert environment (see inset of Figure 1) and is one of Peru's largest agricultural developments. While meteoric water supply is limited by an average annual rainfall of 17 mm per year [23], snow melt from the Andes Mountains rising to the east provides a significant water source for agricultural irrigation and development through both the adjoining deeply incised Siguas River valley as well as a system of purpose-built irrigation aqueducts. The Majes I irrigation project has significantly contributed to the overall local food supply and created jobs; however, it also has affected the local hydrology and groundwater table and is suspected of contributing to a recent increase in landslide activities in the Siguas River valley [24][25][26].…”