Screening variability and change of soil moisture under wide-ranging climate conditions : Snow dynamics effects

Acknowledgments This work has been supported by the Stockholm University strategic environmental research program Ekoklim and The Swedish Research Council Formas (project 2012-790).Peer reviewedPublisher PD

Screening long-term variability and change of soil moisture in a changing climate

Acknowledgments We acknowledge support for this work from the Swedish Research Council (VR; Project Number 2009-3221), and the strategic research program Ekoklim at Stockholm University.Peer reviewedPublisher PD

Data-model comparison of temporal variability in long-term time series of large-scale soil moisture

Acknowledgments This work has been supported by the Swedish University strategic environmental research program Ekoklim and the Swedish Research Council Formas (project 2012-790). The soil moisture data were downloaded from the Ameriflux website: funding for AmeriFlux data resources was provided by the U.S. Department of Energy's Office of Science. GPCC Precipitation data, GHCN Gridded V2 data, NARR data, and CPC US Unified Precipitation data were obtained from the Web site of NOAA/OAR/ESRL PSD, Boulder, Colorado, USA, at http://www.esrl.noaa.gov/psd/.Peer reviewedPublisher PD

Opportunities and challenges in using catchment-scale storage estimates from cosmic ray neutron sensors for rainfall-runoff modelling

Acknowledgements We thank the Macaulay Development Trust and School of Geosciences, University of Aberdeen for KDPs scholarship. JG would like to acknowledge funding from the Royal Society and the Carnegie Trust for the Universities of Scotland (project 70112). JG and LV acknowledge funding from the UK Natural Environment Research Council (project NE/N007611/1 and CC13_080). MW was supported by the Rural & Environment Science & Analytical Services Division of the Scottish Government. RR received funding from the Natural Environment Research Council (projects NE/M003086/1, NE/R004897/1 and NE/T005645/1) and from the International Atomic Energy Agency of the United Nations (IAEA/UN) (project CRP D12014). Special thanks to Carol Taylor, Jessica Fennell, Alice Poli and many more for assistance with fieldwork. Finally, we would like to acknowledge Kenneth Loades for providing us with essential equipment for soil sampling and thank David Finlay and his team for enabling land access in Elsick.Peer reviewedPostprin

Importance of short-term temporal variability in soil physical properties for soil water modelling under different tillage practices

Acknowledgements This study was part of the Red Soils CZO and MIDST-CZ projects funded by the National Environment Research Council (grants NE/N007611/1 and NE/S009167/1) and the National Sciences Foundation of China (NSFC: 41571130051, 41571130053, 41371235). The 596 experiments in Scotland had financial support from the Rural & Environment Science & Analytical Services Division of the Scottish Government.Peer reviewedPostprin

A Simple Modelling Framework for Shallow Subsurface Water Storage and Flow

Water storage and flow in shallow subsurface drives runoff generation, vegetation water use and nutrient cycling. Modelling these processes under non-steady state conditions is challenging, particularly in regions like the subtropics that experience extreme wet and dry periods. At the catchment-scale, physically-based equations (e.g., Richards equation) are impractical due to their complexity, while conceptual models typically rely on steady state assumptions not found in daily hydrological dynamics. We addressed this by developing a simple modelling framework for shallow subsurface water dynamics based on physical relationships and a proxy parameter for the fluxes induced by non-unit hydraulic gradients. We demonstrate its applicability for six generic soil textures and for an Acrisol in subtropical China. Results showed that our new approach represents top soil daily fluxes and storage better than, and as fast as, standard conceptual approaches. Moreover, it was less complex and up to two orders of magnitude faster than simulating Richards equation, making it easy to include in existing hydrological models

Modeling long-term variability and change of soil moisture and groundwater level - from catchment to global scale

The water stored in and flowing through the subsurface is fundamental for sustaining human activities and needs, feeding water and its constituents to surface water bodies and supporting the functioning of their ecosystems. Quantifying the changes that affect the subsurface water is crucial for our understanding of its dynamics and changes driven by climate change and other changes in the landscape, such as in land-use and water-use. It is inherently difficult to directly measure soil moisture and groundwater levels over large spatial scales and long times. Models are therefore needed to capture the soil moisture and groundwater level dynamics over such large spatiotemporal scales. This thesis develops a modeling framework that allows for long-term catchment-scale screening of soil moisture and groundwater level changes. The novelty in this development resides in an explicit link drawn between catchment-scale hydroclimatic and soil hydraulics conditions, using observed runoff data as an approximation of soil water flux and accounting for the effects of snow storage-melting dynamics on that flux. Both past and future relative changes can be assessed by use of this modeling framework, with future change projections based on common climate model outputs. By direct model-observation comparison, the thesis shows that the developed modeling framework can reproduce the temporal variability of large-scale changes in soil water storage, as obtained from the GRACE satellite product, for most of 25 large study catchments around the world. Also compared with locally measured soil water content and groundwater level in 10 U.S. catchments, the modeling approach can reasonably well reproduce relative seasonal fluctuations around long-term average values. The developed modeling framework is further used to project soil moisture changes due to expected future climate change for 81 catchments around the world. The future soil moisture changes depend on the considered radiative forcing scenario (RCP) but are overall large for the occurrence frequency of dry and wet events and the inter-annual variability of seasonal soil moisture. These changes tend to be higher for the dry events and the dry season, respectively, than for the corresponding wet quantities, indicating increased drought risk for some parts of the world