Global-scale nitrogen budgets developed to quantify anthropogenic impacts on the nitrogen cycle do not explicitly consider nitrate stored in the vadose zone. Here we show that the vadose zone is an important store of nitrate that should be considered in future budgets for effective policymaking. Using estimates of groundwater depth and nitrate leaching for 1900–2000, we quantify the peak global storage of nitrate in the vadose zone as 605–1814 Teragrams (Tg). Estimates of nitrate storage are validated using basin-scale and national-scale estimates and observed groundwater nitrate data. Nitrate storage per unit area is greatest in North America, China and Europe where there are thick vadose zones and extensive historical agriculture. In these areas, long travel times in the vadose zone may delay the impact of changes in agricultural practices on groundwater quality. We argue that in these areas use of conventional nitrogen budget approaches is inappropriate.

Abstract. We present the first large-sample catchment hydrology dataset for Great Britain, CAMELS-GB (Catchment Attributes and MEteorology for Large-sample Studies). CAMELS-GB collates river flows, catchment attributes and catchment boundaries from the UK National River Flow Archive together with a suite of new meteorological time series and catchment attributes. These data are provided for 671 catchments that cover a wide range of climatic, hydrological, landscape, and human management characteristics across Great Britain. Daily time series covering 1970–2015 (a period including several hydrological extreme events) are provided for a range of hydro-meteorological variables including rainfall, potential evapotranspiration, temperature, radiation, humidity, and river flow. A comprehensive set of catchment attributes is quantified including topography, climate, hydrology, land cover, soils, and hydrogeology. Importantly, we also derive human management attributes (including attributes summarising abstractions, returns, and reservoir capacity in each catchment), as well as attributes describing the quality of the flow data including the first set of discharge uncertainty estimates (provided at multiple flow quantiles) for Great Britain. CAMELS-GB (Coxon et al., 2020; available at https://doi.org/10.5285/8344e4f3-d2ea-44f5-8afa-86d2987543a9) is intended for the community as a publicly available, easily accessible dataset to use in a wide range of environmental and modelling analyses.

Abstract:A simple process-based approach to predict regional-scale loading of nitrate at the water table was implemented in a GIS for Great Britain. This links a nitrate input function, unsaturated zone thickness and lithologically-dependent rate of nitrate unsaturated zone travel to estimate arrival time of nitrate at the water table. The nitrate input function is the loading at the base of the soil and has been validated using unsaturated zone pore-water profiles. The unsaturated zone thickness uses groundwater levels based on regional-scale observations infilled by interpolated river base levels. Estimates of the rate of unsaturated zone travel are attributed from regional-scale hydrogeological mapping. The results indicate that peak nitrate loading may have already arrived at the water table for many aquifers, but that it has not where the unsaturated zone is relatively thick There are contrasting outcomes for the two main aquifers which have similar unsaturated zone velocities, the predominantly low relief Permo-Triassic sandstones and the Chalk, which forms significant topographic features. For about 60% of the Chalk, the peak input has not yet reached the water table and will continue to arrive over the next 60 years. The methodology is readily transferable and provides a robust method for estimating peak arrival time for any diffuse conservative pollutant where an input function can be defined at a regional scale and requires only depth to groundwater and a hydrogeological classification. The methodology is extendable in that if additional information is available this can easily be incorporated into the model scheme.

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The performance of an open or closed loop ground source heat pump system depends on local geological conditions. It is important these are determined as accurately as possible when designing a system in order to maximise efficiency and minimise installation costs.Factors that need to be considered are surface temperature, sub-surface temperatures down to 100 -200 m, thermal conductivities and diffusivities of the soil and rock layers, groundwater levels and flows and aquifer properties. In addition rock strength is a critical factor in determining the excavation or drilling method required at a site and the associated costs. The key to determining all of these factors is an accurate conceptual site scale model of the ground conditions (soils, geology, thermogeology, engineering geology and hydrogeology).The British Geological Survey has used the modern digital geological mapping of the UK as a base onto which appropriate attributes can be assigned. As a result it is possible to generate regional maps of surface and sub-surface temperatures, rock strength and depth to water. This information can be used by designers, planners and installers of ground source heat pump systems. The use of appropriate geological factors will assist in creating a system that meets the heating or cooling load of the building without unnecessary over engineering.2