The SPLASH Action Group—Towards standardized sampling strategies in permafrost science

The Action Group called‘Standardized methods across Permafrost Landscapes:from Arctic Soils to Hydrosystems’(SPLASH)is a community-driven effort aiming to provide a suite of standardized field strategies for sampling mineral and organic components in soils,sediments,and water across permafrost landscapes.This unified approach will allow data from different landscape interfaces,field locations and seasons to be shared and compared,thus improving our understanding of the processes occurring during lateral transport in circumpolar Arctic watersheds.

Hand-feel soil texture observations to evaluate the accuracy of digital soil maps for local prediction of soil particle size distribution:A case study in Central France

Digital maps of soil properties are now widely available.End-users now can access several digital soil mapping(DSM)products of soil properties,produced using different models,calibration/training data,and covariates at various spatial scales from global to local.Therefore,there is an urgent need to provide easy-to-understand tools to communicate map uncertainty and help end-users assess the reliability of DSM products for use at local scales.In this study,we used a large amount of hand-feel soil texture(HFST)data to assess the performance of various published DSM products on the prediction of soil particle size distribution in Central France.We tested four DSM products for soil texture prediction developed at various scales(global,continental,national,and regional)by comparing their predictions with approximately 3200 HFST observations realized on a 1:50000 soil survey conducted after release of these DSM products.We used both visual comparisons and quantitative indicators to match the DSM predictions and HFST observations.The comparison between the low-cost HFST observations and DSM predictions clearly showed the applicability of various DSM products,with the prediction accuracy increasing from global to regional predictions.This simple evaluation can determine which products can be used at the local scale and if more accurate DSM products are required.

Surface storm flow prediction on hillslopes based on topography and hydrologic connectivity

Background:Hillslopes provide critical watershed ecosystem services such as soil erosion control and storm flow regulation through collecting,storing,and releasing rain water.During intense rainstorms,rainfall intensity and infiltration capacity on the hillslope control Hortonian runoff while the topographic attributes of the hillslope(e.g.,slope,aspect,curvature)and the channel network define the structural hydraulic connectivity that determines how rapidly excess water is transferred.This paper discusses literature on the link between topographic attributes and hydrologic connectivity and demonstrates how this link can be used to define a parsimonious model for predicting surface runoff during high intensity rainfall.Main text:First,we provide a topographic characterization of the hillslope necessary to determine the structural hydrologic connectivity of surface flow based on existing literature.Subsequently,we demonstrate a hydrologic surface response model that routes the geomorphologic unit hydrograph(GIUH)through a spatial domain of representative elementary hillslopes reflecting the structural hydrologic connectivity.Topographic attributes impact flow and travel time distributions by affecting gravitational acceleration of overland flow and channel,solar irradiance,flow deceleration by vegetation,and flow divergence/convergence.Conclusions:We show with an example where we apply the GIUH-based model to hypothetical hillslopes that the spatial organization of the channel network is critical in the flow and travel time distribution,and that topographic attributes are key in obtaining simple yet accurate representations of hydrologic connectivity.Parsimonious GIUH models of surface runoff that use this hydrologic connectivity have the advantage of low data requirements,being scalable and applicable regardless of the spatial complexity of the hillslope,and have the potential to fundamentally improve flood forecasting tools used in the assessment of ecosystem services.

Distinct and combined impacts of climate and land use scenarios on water availability and sediment loads for a water supply reservoir in northern Morocco

The objective of this study was to examine the impacts of climate and land use changes on wateravailability and sediment loads for a water supply reservoir in northern Morocco using data-intensive simulation models in a data-scarce region. Impacts were assessed by comparing the simulated water and sediment entering the reservoir between the future period 2031-2050 and the 1983-2010 reference period. Three scenarios of land use change and two scenarios of climate change were developed in the Tleta watershed. Simulations under current and future conditions were performed using the Soil and Water Assessment Tool (SWAT) model. The simulations showed that climate change will lead to a sig-nificant decrease in the annual water supply to the reservoir (-16.9% and -27.5%) and in the annual volume of sediment entering the reservoir (-7.4% and -12.6%), depending on the climate change sce-narios tested. The three scenarios of land use change will lead to a moderate change in annual water inflow into the reservoir (between-6.7% and +6.2%), while causing a significant decrease in sediment entering the reservoir (-37%to-24%). The combined impacts of climate and land use changes will cause a reduction in annual water availability (-9.9%to-33.3%) and sediment supplies (-28.7%to-45.8%). As a result, the lifetime of the reservoir will be extended, but at the same time, the risk of water shortages will increase, especially from July to March. Therefore, alternative water resources must be considered.