Assessment of current and future water availability for agriculture and terrestrial ecosystems under different land-use scenarios over the aconcagua basin: toward drought adaptation

Folio: 3230678

drought

Abstract

Drought is recognized as a slow-onset natural hazard that originates from a deficiency of rainfall over a prolonged period and is also described as an inequality of water accessibility. It is known as the global costliest climatic hazard that destroys the agriculture and ecosystem in terms of economy, society, and nature. The intensity and frequency of droughts have increased over the past decades and this trend has continued in the 21st century. On the other hand, climate and cropping patterns changes are two main factors that directly influence basin hydrological processes, affecting such as ET, surface runoff, interception and infiltration and agricultural production. Therefore, hydrological modelling provides a physical-based framework to investigate the relationships among land use change and hydrologic processes, crop production and water productivity. The main efforts in Chile have analyzed the hydrological response to land use scenarios, focused on forest expansion, but related to the availability-demand of crops and ecosystems in combined future land use and climate changes to adapt to drought, it is still limited. Terrestrial ecosystems are closely connected through delivery of water, growth consumes large amounts of water through transpiration, and critically affects soil moisture dynamics, therefore, different vegetation coverages have key impacts on eco-hydrological processes. Thus, it is essential to consider vegetation coverage when simulating eco-hydrological processes. In this sense, few research have focus on water availability-demand of terrestrial ecosystems over future land use-cover scenarios under a drought context.

Since 2010, Central Chile has been experiencing an uninterrupted sequence of dry years that has been classified as Mega-drought. The observed decline in rainfall over central Chile has been greatly accentuated with annual rainfall deficits, diminished Andean snowpack, river discharge, reservoir volumes, groundwater levels, greater evapotranspiration (ET) from crops and natural vegetation. As a result, pumping groundwater from aquifers of Valparaiso region are increasing to support mainly intensive agriculture activities. The Aconcagua River provides water for agriculture, mining, and industry and freshwater for human consumption for the 1.7 million inhabitants of the Valparaíso Region, and the withdrawal for agriculture exceeds the 88%. The water availability-demand related to all hydrological cycle and the extension of agricultural land, are poorly investigated to date, and even less considering the integrity of terrestrial ecosystems in this basin. The lack of this consensus generates uncertainty about the future water demand in the Aconcagua basin in times of mega-drought. Therefore, the decision made on the future land use will be critical to achieving the United Nations 2030 Agenda for the Sustainable Development Goals (SDGs). The aforementioned problem will be evaluated in this research, analyzing the hydrological process in terms of availability-demand of crops (avocado and grape) and terrestrial ecosystems (native forest, grassland and scrub) in past, present and future land use-cover scenarios, using a SWAT hydrological model and in future climate change scenarios. Climatic and hydrological data will be used, such as snow cover, topographic parameters, land type and use, and satellite images . Determining these hydrological changes on crops and ecosystems in future land use-cover scenarios will lay the foundations for decision-making to adapt to drought and contribute to the sustainable management of water resources in the Aconcagua basin and in Chile.