Analyze from a holistic and comprehensive perspective the water resource in the water cycle context and its relationships in the various environments for the strategic approach to resilience as a way to sustainability.
Freshwater represents a small fraction of the available water on earth . With water demand growing approximately 1% per year since the 1980s , global demand for the vital resource will continue to increase at a similar rate until 2050 and rise from 20% to 30% above the current use level . Among the leading causes of increased water demand is the growth of the world population (urbanization), changes in consumption patterns (e.g., product preferences based on meat and sugar), improvement of living standards (economic growth, industrialization), and expansion of irrigated agriculture (increased production) .
Water resource exploitation, in combination with the intersecting effects of climate change  due to human activity, demarcates a new geological epoch (the Anthropocene) . These factors have led to a shortage crisis scenario of unsustainable use of water, a global issue demonstrating that two-thirds of the world population experience severe water shortage conditions at least one month a year . The alarming evidence has led to the creation of strategies to face water scarcity, focusing on its practical and sustainable management .
The first known scientific use in English of the word 'resilience' is attributed to Francis Bacon , who used it in the 17th century to describe the way an echo bounces back from a wall. In general, resilience is defined by the Oxford English Dictionary as (i) the capacity to recover quickly from difficulties, and (ii) the ability of a substance or object to spring back into shape . For Timmerman , in the domain of engineering and disasters, resilience is the ability of human communities to withstand external shocks or perturbations to their infrastructure and to recover from such perturbations. In the social and ecological domain, Holling  defined it as the amount of disturbance that can be sustained by a system before a change occurs in its mechanisms of control or its structure. Regarding groundwater systems, Sharma and Sharma  defined resilience as the ability of the system to maintain groundwater reserves despite significant disturbances.
Resilience is known as the adaptive capacity of a system to a change generated by external pressures while maintaining certain vital functions. This concept has gained a prominent place in water policies, ranging from water resource management at the hydrographic basin scale, to drought and flood management, to climate change adaptation in the water services sector (e.g., , , , , , , , ). In the human–water interaction context, three types of systems and subsystems in the framework of resilience emerge: (i) the water subsystem, with hydrological resilience to anthropogenic risks; (ii) the human subsystem, with social resilience to hydrological risks; and (iii) the socio-hydrological subsystem, with socio-hydrological resilience .
Defining and understanding the system is key to any assessment of resilience   . Hence, knowing the system allows examination of its state, evolution, and variables. Thus, the evaluation leads to the proposal of strategies/measures for reaching the desired state.
Several authors have used numerical methods   or the water storage variability in a period  to assess the resilience of groundwater systems during droughts. Peters et al.  evaluated the performance of groundwater systems in the event of drought using three indicators: resilience, reliability, and vulnerability. In the Pang Basin (United Kingdom), a similar study was carried out by Hugman et al. . In the Querença–Silves aquifer system (Portugal), a quantitative evaluation of aquifer performance and its resilience or recovery capacity was carried out based on four sustainable performance factors: property, recharge, pumping, and distribution of wells in aquifers. Another study, on a larger scale, used remote sensing satellites to assess resilience. The study made use of NASA’s Gravity and Recovery and Climate Experiment (GRACE) tool to assess groundwater resilience based on global estimates of groundwater storage and average flow subsurface net storage. The authors defined the total groundwater stress ratio as a measure of groundwater resilience that applies to large aquifers only .
Water resilience must be comprehensively evaluated beyond the recharge capacity or economic impact of significant changes in the system. The analysis must include physical, environmental, economic, and social impacts.
There are many ways to assess sustainable development; indicators are among the most commonly used approaches . Studies have been presented in the water context based on the development of indicators to measure the sustainability and resilience of different aspects of these systems. Some examples are the development of the water provision resilience indicator, a measure of the capacity of the water system to maintain or improve the percentage of the population with access to safe water in the water supply sector (supply, infrastructure, service provision, finance, water quality, and governance) ; the application of a framework of nine indicators of water resource management at the level of the watershed (water quality, water quantity, system stability, water-use efficiency, user-sector productivity, institutional preparedness, equitable water services, water-related well-being, public participation) ; the use of indicators of wastewater treatment systems for sustainability assessment, highlighting key indicators such as organic matter, nutrients, cost, heavy metals, and land area , the work proposed by Polonenko et al.  studying indicators within the role of institutions and communities in urban water systems, as well as indicators for various areas such as social, institutional, governance, economic, technological, and environmental, especially in such systems , , , . Finally, GRAM matrix for assessing water resilience based on indicators in the Sustainable Development Goals (SDGs) and the four axes of development (political, social, environmental, and cultural) in a communal coastal aquifer system proposed by Herrera-Franco et al., .
For groundwater sustainability, it is essential to know the factors that influence recharge: (i) climate, (ii) geology and topography, and (iii) land cover and use, adapting them to the four axes of sustainability: (i) political and economic, (ii) environmental, (iii) social, and (iv) cultural. The positive interaction of all these aspects makes the socio-hydrological system resilient, satisfying the demand for water in the face of demographic explosion and climate change.
Resilience can be taught and improved if there is a methodology that benchmarks, measures, and indicates its strengths, good practices, and acute problems. Therefore, it will be possible to implement long-term measures that solve system problems.