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Modelling the water balance of Lake Victoria (East Africa) – Part 1: Observational analysis

Lake Victoria is the largest lake in Africa and one of the two major sources of the Nile river. The water level of Lake Victoria is determined by its water balance, consisting of lake precipitation and evaporation, inflow from rivers and lake outflow, controlled by two hydropower dams. Here, we present a water balance model for Lake Victoria, which closely represents the observed lake levels. The model results highlight the sensitivity of the lake level to human operations at the dam.

Modelling the water balance of Lake Victoria (East Africa) – Part 2: Future projections

Lake Victoria is the second largest freshwater lake in the world and one of the major sources of the Nile River, which is controlled by two hydropower dams. In this paper we estimate the potential consequences of climate change for future water level fluctuations of Lake Victoria. Our results reveal that the operating strategies at the dam are the main controlling factors of future lake levels and that regional climate simulations used in the projections encompass large uncertainties.

The importance of small artificial water bodies as sources of methane emissions in Queensland, Australia

Artificial water bodies are a major source of methane and an important contributor to flooded land greenhouse gas emissions. Past studies focussed on large water supply or hydropower reservoirs with small artificial water bodies (ponds) almost completely ignored. This regional study demonstrated ponds accounted for one-third of flooded land surface area and emitted over 1.6 million t CO₂eq. yr⁻¹(10 % of land use sector emissions). Ponds should be included in regional GHG inventories.

Why has catchment evaporation increased in the past 40 years? A data-based study in Austria

We analyze changes in catchment evaporation estimated from the water balances of 156 catchments in Austria over 1977–2014, as well as the possible causes of these changes. Our results show that catchment evaporation increased on average by 29 ± 14 mm yr⁻¹ decade⁻¹. We attribute this increase to changes in atmospheric demand (based on reference and pan evaporation), changes in vegetation (quantified by a satellite-based vegetation index), and changes in precipitation.

Global 5 km resolution estimates of secondary evaporation including irrigation through satellite data assimilation

Evaporation from wetlands, lakes and irrigation areas needs to be measured to understand water scarcity. So far, this has only been possible for small regions. Here, we develop a solution that can be applied at a very high resolution globally by making use of satellite observations. Our results show that 16% of global water resources evaporate before reaching the ocean, mostly from surface water. Irrigation water use is less than 1% globally but is a very large water user in several dry basins.

Speculations on the application of foliar ¹³C discrimination to reveal groundwater dependency of vegetation and provide estimates of root depth and rates of groundwater use

Groundwater is a significant water resource for humans and for groundwater-dependent vegetation. Several challenges to managing both groundwater resources and dependent vegetation include defining the location of dependent vegetation, the rate of groundwater use, and the depth of roots accessing groundwater. In this study we demonstrate a novel application of measurements of stable isotopes of carbon that can be used to identify the location, the rooting depth, and the rate of groundwater use.

Estimating time-dependent vegetation biases in the SMAP soil moisture product

Satellite soil moisture products can provide critical information on incipient droughts and the interplay between vegetation and water availability. However, time-variant systematic errors in the soil moisture products may impede their usefulness. Using a novel statistical approach, we detect such errors (associated with changing vegetation) in the SMAP soil moisture product. The vegetation-associated biases impede drought detection and the quantification of vegetation–water interactions.

On the dynamic nature of hydrological similarity

In this study we explore the role of spatially distributed information on hydrological modeling. For that, we develop and test an approach which draws upon information theory and thermodynamic reasoning. We show that the proposed set of methods provide a powerful framework for understanding and diagnosing how and when process organization and functional similarity of hydrological systems emerge in time and, hence, when which landscape characteristic is important in a model application.

Inter-laboratory comparison of cryogenic water extraction systems for stable isotope analysis of soil water

To extract water from soils for isotopic analysis, cryogenic water extraction is the most widely used removal technique. This work presents results from a worldwide laboratory intercomparison test of cryogenic extraction systems. Our results showed large differences in retrieved isotopic signatures among participating laboratories linked to interactions between soil type and properties, system setup, extraction efficiency, extraction system leaks, and each lab’s internal accuracy.

HESS Opinions: Science in today’s media landscape – challenges and lessons from hydrologists and journalists

Media play a key role in the communication between scientists and the general public. However, the interaction between scientists and journalists is not always straightforward. In this opinion paper, we present insights from hydrologists and journalists into the benefits, aftermath and potential pitfalls of science–media interaction. We aim to encourage scientists to participate in the diverse and evolving media landscape, and we call on the scientific community to support scientists who do so.

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