Surface Water and Groundwater Systems under Hydroclimatic Non-Stationarity

Surface water and groundwater are components of a single hydrological system, yet the assumption that their behavior fluctuates around a stable long-term mean no longer holds. Under a changing climate, shifting precipitation and temperature regimes, evolving land and water use, and an increasing frequency of extremes are pushing hydrological systems into non-stationary behavior, with trends, change points, and regime shifts that conventional stationary approaches fail to capture. Human water management is itself part of this picture: management practices evolve under a changing climate and introduce their own non-stationarity into the system. This Research Topic takes hydroclimatic non-stationarity as the essential lens for interpreting how these systems respond, interact, and evolve.The central scientific question is: what are the implications of hydroclimatic non-stationarity for surface water and groundwater systems, and at what temporal and spatial scales?To keep the collection coherent and distinct, hydroclimatic non-stationarity must be the central analytical framework of every contribution. We invite studies that explicitly detect, quantify, attribute, or model non-stationarity (for example trends, change points, regime shifts, or evolving distributions and dependence structures) in surface water systems, groundwater systems, or their interaction. Studies that address coupled surface water–groundwater behavior are of particular interest, but high-quality contributions focused primarily on either surface water or groundwater are equally welcome, provided non-stationarity remains the central analytical theme. This explicitly includes weakly coupled or decoupled systems, such as those in arid and semi-arid regions, where deep water tables or ephemeral flows limit interaction yet non-stationarity is pronounced.Studies that assume stationarity, or in which non-stationarity is incidental rather than central, fall outside the scope.Themes of interest include, but are not limited to:• Detection, attribution, and modeling of non-stationarity in hydroclimatic and hydrological variables• Non-stationary surface water–groundwater interactions, exchange fluxes, and connectivity• Changing surface water–groundwater connectivity, including weakening or intermittent coupling, under non-stationary conditions• Streamflow regimes and variability under evolving hydroclimatic conditions, including ephemeral and regulated rivers• Groundwater recharge and storage dynamics under non-stationary forcing• Shifting drought and flood regimes and their propagation through hydrological systems• Non-stationarity in water quantity and quality, and coupled hydrologic–hydrogeochemical processes• Non-stationarity introduced by evolving water management practices under a changing climate• Scale dependence of non-stationary responses across temporal and spatial scales• Methods, frameworks, and data (including long records and models) for characterizing non-stationarityWe welcome papers that advance understanding of surface water and groundwater systems through an explicit non-stationarity framework. Topic editors: Naser Almanaseer, Naresh Devineni Source: https://www.frontiersin.org/research-topics/84885/surface-water-and-groundwater-systems-under-hydroclimatic-non-stationarity