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Modeling 25 years of spatio-temporal surface water and inundation dynamics on large river basin scale using time series of Earth observation data

We statistically modeled surface water extent (SWE) and inundation dynamics from a unique Landsat-based time series (1986–2011) for Australia’s Murray–Darling Basin as a function of river flow and spatially explicit time series of rainfall, evapotranspiration and soil moisture. We present a data-driven and transferable approach that allowed us to model SWE through periods of flooding and drying for 363 floodplain units and to identify local combinations of variables that drive SWE dynamics.

Investigating the impact of land-use land-cover change on Indian summer monsoon daily rainfall and temperature during 1951–2005 using a regional climate model

Regional climate model (RegCM4) simulations demonstrate that part of the observed decrease in moderate rainfall events during the summer monsoon season over central India from 1951 to 2005 is attributed to anthropogenically induced land-use land-cover change (LULCC). LULCC also partly explains the observed warming trend in the daily mean and maximum temperatures over India. This study demonstrates the importance of LULCC in the context of regional climate change over India.

Coevolution of volcanic catchments in Japan

We derived indices of landscape properties as well as hydrological response and examined their relation with catchment age and climate. We found significant correlation between drainage density and baseflow index with age, but not with climate. We compared our data with data from volcanic catchments in Oregon and could confirm that baseflow index decreases with time, but also discovered that drainage density seems to stabilize after 2M years, after an initial increase due to landscape incision.

Does the Budyko curve reflect a maximum-power state of hydrological systems? A backward analysis

We derived mathematical formulations of relations between relative wetness and gradients driving run-off and evaporation for a one-box model such that, when conductances are optimized with the maximum power principle, the model leads exactly to a point on the Budyko curve. With dry spells and dynamics in actual evaporation added, the model compared well with catchment observations without calibrating any parameter. The maximum-power principle may thus be used to derive the Budyko curve.

Aggregation in environmental systems – Part 1: Seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments

Catchment mean transit times have been widely inferred from seasonal cycles of environmental tracers in precipitation and streamflow. Here I show that these cycles yield strongly biased estimates of mean transit times in spatially heterogeneous catchments (and, by implication, in real-world catchments). However, I also show that these cycles can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago.

Aggregation in environmental systems – Part 2: Catchment mean transit times and young water fractions under hydrologic nonstationarity

Here I show that seasonal tracer cycles yield strongly biased estimates of mean transit times in nonstationary catchments (and, by implication, in real-world catchments). However, they can be used to reliably estimate the fraction of “young” water in streamflow, meaning water that fell as precipitation less than roughly 2–3 months ago. This young water fraction varies systematically between high and low flows and may help in characterizing controls on stream chemistry.

Diagnosing hydrological limitations of a land surface model: application of JULES to a deep-groundwater chalk basin

This paper presents a strategy to diagnose hydrological limitations of a Land Surface Model. It includes the adaptation of the model for hydrological applications and highlights challenges faced while moving towards high resolution modelling.

Regional analysis of groundwater droughts using hydrograph classification

To improve the design of drought monitoring networks and water resource management during episodes of drought, there is a need for a better understanding of spatial variations in the response of aquifers to major meteorological droughts. This paper is the first to describe a suite of methods to quantify such variations. Using an analysis of groundwater level data for a case study from the UK, the influence of catchment characteristics on the varied response of groundwater to droughts is explored.

Towards observation-based gridded runoff estimates for Europe

Water storages and fluxes on land are key variables in the earth system. To provide context for local investigations and to understand phenomena that emerge at large spatial scales, information on continental freshwater dynamics is needed. This paper presents a methodology to estimate continental scale runoff on a 0.5° spatial grid, which combines the advantages of in-situ observations with the power of machine learning regression. The resulting runoff estimates compare well with observations.

Large-basin hydrological response to climate model outputs: uncertainty caused by internal atmospheric variability

Our paper is one of very few studies where the influence of stochastic internal atmospheric variability (IAV) on the hydrological response is analyzed. On the basis of ensemble experiments with GCM and hydrological models, we found, e.g., that averaging over ensemble members filters the stochastic term related to IAV, and that a considerable portion of the simulated trend in annual Lena R. runoff can be explained by the externally forced signal (global SST and SIC changes in our experiments).

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