Fewer Basins Will Follow Their Budyko Curves Under Global Warming and Fossil‐Fueled Development

The Budyko framework consists of a curvilinear relationship between the evaporative ratio (i.e., actual evaporation over precipitation) and the aridity index (i.e., potential evaporation over precipitation) and defines evaporation's water and energy limits. A basin's movement within the Budyko space illustrates its hydroclimatic change and helps identify the main drivers of change. On the one hand, long-term aridity changes drive evaporative ratio changes, moving basins along their Budyko curves. On the other hand, historical human development can cause river basins to deviate from their curves. The question is if basins will deviate or follow their Budyko curves under the future effects of global warming and related human developments. To answer this, we quantify the movement in the Budyko space of 405 river basins from 1901–1950 to 2051–2100 based on the outputs of seven models from the Coupled Model Intercomparison Project - Phase 6 (CMIP6). We account for the implications of using different potential evaporation models and study low- and high-emissions scenarios. We find considerable differences of movement in Budyko space regarding direction and intensity when using the two estimates of potential evaporation. However, regardless of the potential evaporation estimate and the scenario used, most river basins will not follow their reference Budyko curves (>72%). Furthermore, the number of basins not following their curves increases under high greenhouse gas emissions and fossil-fueled development SP585 and across dry and wet basin groups. We elaborate on the possible explanations for a large number of basins not following their Budyko curves

Comparative Hydrology Across Physiographic and Climatic Diversity: A search for simple patterns and predictability

The bulk of catchment science literature consist of ‘unique’ case studies describing the complex interaction of soils, water, vegetation, topography and geology at individual sites. Yet, the uniqueness of individual sites makes it difficult to transfer findings to new locations and facilitate understanding and prediction in other catchments. In this thesis we use a comparative approach by searching for general behaviour among several hundred catchments located across the contiguous United States to develop transferable theories and facilitate understanding and prediction at other sites. The thesis consist of an introduction to elucidate the use of the comparative approach. Subsequently we present three chapters that use this comparative approach to test multiple hypotheses. (I) We search for appropriate model structures to facilitate improved precipitation-streamflow simulations at the catchment scale. Results indicate that several catchment properties can support the choice for appropriate model structures but choices are associated with large uncertainty. (II) We develop an analytical framework to organise the seasonal partitioning of water for a wide range of settings and show how this framework can facilitate in synthesising understanding of catchment functioning for a wide range of time-scales. (III) We expose how snowfall influences the partitioning of water at the annual time-scale. Results indicate that the projected precipitation shift from snowfall to rain, due to global rising temperatures, may significantly decrease the annual streamflow of catchments that currently receive a large fraction of their precipitation as snowfall. Finally, we conclude that although findings of the individual chapters are valuable, physical understanding is lacking. Additionally there is no common framework to organise the findings within the context of other studies. Both aspects hamper practical and scientific progress to effectively handle many water-related challenges.Water ManagementCivil Engineering and Geoscience

The development of an autonomous GPS system to monitor tidal slack in estuaries

Recently, a promising method for measuring tidal slack using GPS receivers attached to buoys has been tested. The next step is to build a wireless GPS system which conducts measurements continuous and real-time. This research primarily focuses on the development of the hardware of that GPS system. Secondly it focuses on modeling the buoy behavior and calculation algorithms for determining the moment of slack. A series of GPS measurements are conducted to test the accuracy and precision of candidate receivers. For the hardware a Waspmote-board and Meshlium router are chosen. Together they provide a complete solution for the GPS system, including GPS receiver. The solution combines adaptability with low costs. The module is made waterproof and solar powered. A buoy model is made with which data sets can be simulated to test the accuracy of the calculation algorithms. The sensitivity tests of the algorithms are performed with a Monte Carlo model. Clear differences in performance between high-end and common receivers are observed. EGNOS improves only the performance of the high-end receiver. The buoys have different behaviour, not all buoys can be modeled the same. Also a bias of up to 10 minutes is found for the calculation algorithms. In terms of sensitivity of the methods, there is a critical standard deviation for the GPS receiver for which the methods become unstable.With all tested GPS receivers the moment of tidal slack can be calculated with a deviation up to 15 minutes. The greatest improvement can be made in reducing the bias in the calculation methods.Water ResourcesWater ManagementCivil Engineering and Geoscience

Global dominance of tectonics over climate in shaping river longitudinal profiles

River networks are striking features engraved into the surface of the Earth, shaped by uplift and erosion under the joint influence of climate and tectonics. How a river’s gradient changes as it descends along its course—its longitudinal profile concavity—varies greatly from one basin to the next, reflecting the interplay between uplift and erosional processes. A recent global analysis has suggested that climatic aridity should be a first-order control on river profile concavity, but the importance of climate relative to other factors has not been tested at global scale. Here, we show, using recent global datasets of climate, river profiles and tectonic activity, that tectonics is much more strongly expressed than climate in global patterns of river profile concavity. River profiles tend to be more strongly concave in tectonically active regions along plate boundaries, reflecting tectonically induced spatial variations in uplift rates. Rank correlations between river profile concavity and four global tectonic proxies (basin-averaged channel gradients, distance to plate boundaries and two measures of seismic activity) are much stronger than those between river concavity and three climate metrics (precipitation, potential evapotranspiration and aridity). We explain the association between tectonic activity and increased river profile concavity through a simple conceptual model of long-term uplift and river incision. These results show that tectonics, and not climate, exerts dominant control on the shape of river longitudinal profiles globally

Global Recharge Data Set Indicates Strengthened Groundwater Connection to Surface Fluxes

© 2022 The Authors.Groundwater is an invaluable global resource, but its long-term viability as a resource for consumption, agriculture, and ecosystems depends on precipitation recharging aquifers. How much precipitation recharges groundwaters varies enormously across Earth's surface, yet recharge rates often remain uncertain. Here we use a global synthesis of field-estimated recharge across six continents to show that globally recharge first-order follows a simple function of climatic aridity. We use this relationship to estimate long-term recharge in energy-limited systems outside of permafrost regions. Our aridity-based recharge estimates are consistent with the global field data but, on average, double previous estimates of global models. Our higher recharge estimates are likely caused by preferential groundwater recharge and discharge occurring at grid scales finer than global models. The higher recharge estimates suggest that more groundwater contributes to evapotranspiration and streamflow than previously represented by global hydrological models and global water cycle diagrams

Practical considerations for enhanced-resolution coil-wrapped Distributed Temperature Sensing (discussion)

Fibre optic Distributed Temperature Sensing (DTS) is widely applied in earth sciences. Many applications require a spatial resolution higher than the provided by the DTS instrument. Measurements at these higher resolutions can be achieved with a fibre optic cable helically wrapped on a cylinder. The effect of the probe construction, such as its material, shape, and diameter, on the performance has been poorly understood. In this article, we study datasets obtained from a laboratory experiment using different cable and construction diameters, and three field experiments using different construction characteristics. This study shows that the construction material, shape, diameter, and cable attachment method can have a significant influence on DTS temperature measurements. We present a qualitative and quantitative approximation of errors introduced through the choice of auxiliary construction, influence of solar radiation, coil diameter, and cable attachment method. Our results provide insight into factors that influence DTS measurements, and we present a number of solutions to minimize these errors. These practical considerations allow designers of future DTS measurement setups to improve their environmental temperature measurements.Water ManagementCivil Engineering and Geoscience

Creating Community for Early-Career Geoscientists

The American Geophysical Union (AGU) and the European Geosciences Union (EGU) play central roles in nurturing the next generation of geoscientists. Students and young scientists make up about one quarter of the unions’ active memberships [American Geophysical Union, 2013; European Geosciences Union, 2014], creating a major opportunity to include a new generation of geoscientists as more active contributors to the organizations’ activities, rather than merely as consumers. Both organizations are now explicitly expanding their bottom-up organizational structures to include early-career members (ECMs) by appointing student (AGU) and early-career scientist (EGU) representatives for their scientific divisions. (We refer to “early-career members” because AGU and EGU define student and postdoc members differently). Because this expansion is a recent development, it is still unclear what roles these representatives will play and how these roles will evolve over the coming years. We are ECMs in the hydrological sciences. Here we show how the Young Hydrological Society (YHS) used bottom-up initiatives, aligned closely with the newly appointed AGU and EGU representatives, to help improve the professional development of student and postdoc members by providing opportunities to increase their contributions to the geoscience unions. We call for a conversation on how ECMs can make the best use of these new opportunities to engage proactively with the unions.Water ManagementCivil Engineering and Geoscience