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Web-based distributed volunteer computing enables scientists to constitute platforms that can be used for computational tasks by using potentially millions of computers connected to the internet. It is a widely used approach for many scientific projects, including the analysis of radio signals for signs of extraterrestrial intelligence and determining the mechanisms of protein folding. User adoption and clients' dependence on the desktop software present challenges in volunteer computing projects. This study presents a web-based volunteer computing framework for hydrological applications that requires only a web browser to participate in distributed computing projects. The framework provides distribution and scaling capabilities for projects with user bases of thousands of volunteers. As a case study, we tested and evaluated the proposed framework with a large-scale hydrological flood forecasting model.

There is increasing recognition of the need to incorporate the complex and dynamic interactions between society and water in studies of water resource systems. The study of human-water dynamics requires the involvement of researchers from different disciplines, including hydrology and social science. This paper tracks recent trends in socio-hydrological research using quantitative and qualitative methods. Bibliographic metrics and network analysis are used to identify general trends and illustrate the internal connections in this small but growing interdisciplinary field. Results show that hydrologists dominate research in socio-hydrology as presently defined, with far less participation from social scientists. Research questions for socio-hydrology tend to focus on system dynamics and are often not framed in a way that engages the interests and expertise of social scientists. A qualitative analysis addresses key barriers to the interdisciplinary development of socio-hydrology and identifies research needs and directions for better integration of the human dimensions of water science. Attracting social scientists to this field requires a broader conceptualization of socio-hydrology to focus on sustainable development, risk assessment, hazard management, resilience, adaptation, and knowledge mobilization in addition to hydrology’s traditional focus on systems modeling and decision support. We propose three themes for thematic focus: systemic risk and natural hazards; sustainability science; and adaptive governance. This broader framing of socio-hydrology is inherently more interdisciplinary, brings new methods and viewpoints to the field, and ensures that place-based local values are included in studies of water system dynamics.

This paper deals with hydrological research in regard to the water resources crisis in the vulnerable areas found in the northern part of China. This area includes three main river basins, namely the basins of the Yellow (Huang) River, the Hai River and the Huai River. Several water problems are becoming very severe. Among them, two are the most critical: the Yellow River has been drained dry in the main course of its lower reaches and along its major tributaries, and the groundwater table has rapidly declined in the floodplains of the three rivers' downstream areas. To counter the problems, particularly the critical issues mentioned above, hydrological research, which serves as the basis of water development and management, has been carried out in the last two decades. This paper addresses three basic scientific problems in North China, namely: (a) water consumption and the capacity for saving water; (b) the changes in hydrological processes and water resources caused by natural change and human activities; and (c) the ability to supply water resources and water safety in terms of both quantity and quality within a changing environment. However, opportunities and challenges for ameliorating the problems exist, and new ideas and methodology to solve the problems have been proposed, such as the interface process study on the interactions in the soil-root interface, the plant-atmosphere interface, the soil-atmosphere interface, and the interface of soil water and groundwater. In order to manage water resources in a sustainable manner, the study of water resources' renewal ability as affected by natural change and human activity is addressed from the viewpoint of both water quantity and quality, and their integration. To reduce the vulnerability of water resources in regional water management, a paradigm of sustainable water resources utilization is also proposed, using water-heat balance, water-salt balance, water-sediment balance, and water supply-demand balance. This approach may help reveal the basic problems and point to possible approaches to solving the water problems in North China in the 21st century. Copyright (C) 2004 John Wiley Sons

The use of electrical resistivity tomography (ERT; non-intrusive geophysical technique) was assessed to identify the hydrogeological conditions at a surface water/groundwater test site in the southern Black Forest, Germany. A total of 111 ERT transects were measured, which adopted electrode spacings from 0·5 to 5 m as well as using either Wenner or dipole-dipole electrode arrays. The resulting two-dimensional (2D) electrical resistivity distributions are related to the structure and water content of the subsurface. The images were interpreted with respect to previous classical hillslope hydrological investigations within the same research basin using both tracer methods and groundwater level observations. A raster-grid survey provided a quasi 3D resistivity pattern of the floodplain. Strong structural heterogeneity of the subsurface could be demonstrated, and (non)connectivities between surface and subsurface bodies were mapped. Through the spatial identification of likely flow pathways and source areas of runoff, the deep groundwater within the steeper valley slope seems to be much more connected to runoff generation processes within the valley floodplain than commonly credited in such environmental circumstances. Further, there appears to be no direct link between subsurface water-bodies adjacent to the stream channel. Deep groundwater sources are also able to contribute towards streamflow from exfiltration at the edge of the floodplain as well as through the saturated areas overlying the floodplain itself. Such exfiltrated water then moves towards the stream as channelized surface flow. These findings support previous tracer investigations which showed that groundwater largely dominates the storm hydrograph of the stream, but the source areas of this component were unclear without geophysical measurements. The work highlighted the importance of using information from previous, complementary hydrochemical and hydrometric research campaigns to better interpret the ERT measurements. On the other hand, the ERT can provide a better spatial understanding of existing hydrochemical and hydrometric data. Copyright © 2009 John Wiley & Sons, Ltd.

We want to develop a dialogue between geophysicists and hydrologists interested in synergistically advancing process based watershed research. We identify recent advances in geophysical instrumentation, and provide a vision for the use of electrical and magnetic geophysical instrumentation in watershed scale hydrology. The focus of the paper is to identify instrumentation that could significantly advance this vision for geophysics and hydrology during the next 3–5 years. We acknowledge that this is one of a number of possible ways forward and seek only to offer a relatively narrow and achievable vision. The vision focuses on the measurement of geological structure and identification of flow paths using electrical and magnetic methods. The paper identifies instruments, provides examples of their use, and describes how synergy between measurement and modelling could be achieved. Of specific interest are the airborne systems that can cover large areas and are appropriate for watershed studies. Although airborne geophysics has been around for some time, only in the last few years have systems designed exclusively for hydrological applications begun to emerge. These systems, such as airborne electromagnetic (EM) and transient electromagnetic (TEM), could revolutionize hydrogeological interpretations. Our vision centers on developing nested and cross scale electrical and magnetic measurements that can be used to construct a three-dimensional (3D) electrical or magnetic model of the subsurface in watersheds. The methodological framework assumes a ‘top down’ approach using airborne methods to identify the large scale, dominant architecture of the subsurface. We recognize that the integration of geophysical measurement methods, and data, into watershed process characterization and modelling can only be achieved through dialogue. Especially, through the development of partnerships between geophysicists and hydrologists, partnerships that explore how the application of geophysics can answer critical hydrological science questions, and conversely provide an understanding of the limitations of geophysical measurements and interpretation. Copyright © 2008 John Wiley & Sons, Ltd.

is the combined outcome of both the 2001 EGS ses-sion on the ‘Water balance of mountain basins’ in Nice and the 2002 Annual Meeting of the Ger-man Hydrological Working Group in Berlin. A variety of hydrological and meteorological research top-ics presented at these meetings focused on water resources, modelling, parameterization, remote sens-ing, snow and ice melt, evaporation and transpiration. Case studies concentrated especially on moun-tain areas, which ranged in altitude from 1500 to 6000 m, and on a variety of regions, such asthe Himalayas, Karakorum, Hindukush, Yemen Mountain Massif, Norwegian Scandes and Alps. Theanalysis of water balance components was conducted at many different temporal and spatial scales,ranging from annual and seasonal to daily and hourly, and from entire basins to single lysimetricanalyses.The current discussion about climatic–hydrologic change and bio-adaptability reflects the necessityfor more comprehensive and more detailed knowledge about water balance in mountain basins. Sincemountain watersheds are source areas for large rivers, an understanding of the water balance is invalu-able. This should include a variety of components, such as water input, water storage, water loss, andwater transfer potentials on steep, heterogeneous surfaces. Many of the associated processes are insuf-ficiently investigated, although they are of major significance for both hydrologists and water resourcemanagers.AIMIt is the aim of this special issue to present a diverse range of topics and research areas in order to revealthe wide spectrum of research topics and methods on water balance studies in mountain basins. These stud-ies demonstrate both the success and the emerging difficulties and shortcomings in different research fields.Examples from the developed and from the developing world not only promote comparisons, but also newideas about the availability and transferability of methods.

This paper reports some of the achievements in hydrological research associated with the Mackenzie GEWEX Study (MAGS). MAGS is a multifaceted study of the energy and water cycle in the Mackenzie River Basin, north-western Canada, and emphasizes cold-region processes and modelling. It pursues methodologies of scaling-up process studies to a large river basin that has few measurement sites. This methodology involves new developments, adapting mid-latitude algorithms to the high latitude setting and promoting the use of remote sensing tools for scaling-up. Intensive hydrological process studies have been concentrated at a number of sites. These have been chosen to represent different biophysical facets of the Mackenzie River Basin. They include northern basins in open tundra and at tree-line, a western basin representing the hilly and mountainous western side of the basin, central basin sites of wetlands, Precambrian Shield terrain and the Mackenzie Basin counterpart of the large Laurentian Great Lakes. The most southerly site represents a mixed-wood boreal forest site that is undergoing land-use change as a result of forest harvesting. Regional community model analysis indicates that processes of lee cyclogenesis result in differential input of precipitation across the basin. Significant results centre on models of snow accumulation featuring the role of blowing snow, intercepted snow and snowmelt. These models emphasize the importance of snow patchiness to speed of melt. Snowmelt infiltration into frozen soils is important in controlling runoff, and tundra microlandforms play a unique role in determining the surface runoff characteristics. On the western margins of the basin, there is a very significant difference in the hydrological behaviour of slopes of different aspects as a result of differences in permafrost and vegetation. In the central basin, a deeper understanding of components of the water budget is being gained through stable isotope analysis of wetland waters.

Mountains are fragile ecosystems and globally important as water towers of the earth. Sustainable use of mountains depends upon conservation and optimal use of soil and water resources (Ives & Messerli 1989). Despite regional and global efforts to understand the hydrology of the Himalayan region, soil and water conservation (SWC) programmes in this region mainly rely upon engineering measures. For want of cost-effective vegetative (bioengineering) measures (Deoja et al. 1991), and land use and land cover conducive to SWC, the fragile Himalayan watersheds continue to lose soil and water at alarming rates.

The Niger Delta at the southernmost part of Nigeria, is a large and ecologically sensitive region. Natural and anthropogenic activities, such as subsidence, sea-level rise, upstream dams and reservoirs, dredging and overabstraction of groundwater, disturb this equilibrium, leading to adjustments in ecological conditions and boundaries. Ecological changes affecting large areas cannot be explained by local observation. Relating observed effects to causes of environmental behaviour therefore requires a regionalized data collection, that provides a broader perspective of the issues involved with resultant ease in the identification of common problems and formulation of effective solutions.

Copyright © 2013 John Wiley & Sons, Ltd. Introduction Tropical dry forests have lived in the shadow of their humid counterparts with respect to scientific research. Despite accounting for more than 42% of all tropical forest (Murphy and Lugo, 1995) and roughly 6% of the Earth’s land surface, less than 15% of the literature on all tropical forest research has focused on tropical dry forests with the remainder highlighting work in tropical wet forests (Sanchez-Azofeifa et al., 2005; Santos et al., 2011). Many of these tropical dry forest regions are currently water stressed, and additional pressures from population growth, land use and future climate change will have significant implications for the future functioning of their natural and socioeconomic systems. In spite of the recognized importance ofwater resources in the tropics, there have been remarkably few publications on the hydrological processes in this region as compared to the humid temperate zone (e.g. Bonell, 1993, 1998; Buttle et al., 2009;Ohte andTokuchi, 2011; Price, 2011). This is especially true for tropical dry forests, which is surprising given that surface runoff is often limited to a 3 – 5month period annually, with an intervening dry period with little to no precipitation (Ortiz-Jimenez et al., 2005; Love et al., 2010). Hence, there is a critical need to understand the hydrology of tropical dry forests, particularly in light of current land use and future climate change issues facing these regions. In this, commentary we will highlight the

After several decades of interception studies, there are still considerable gaps in the understanding of wet-canopy evaporation. Model development is being obstructed by the lack of techniques for the measurement of state and rate variables which have to be quantified for model validation. The applicability of microwave attenuation measurements for the determination of canopy wetness is examined. The attenuation caused by a single spruce fir in the laboratory and the vertical attenuation profiles of a Douglas fir stand were measured under dry and wet conditions. The results indicate an instant increase of the attenuation upon wetting and a decrease owing to drip and evaporation after rainfall ceased. From the results, conclusions have been drawn on the design of instrumentation for an optimized measuring system which is suitable for unattended automated scanning of canopy water storage. This system has been calibrated, using vertically integrated microwave attenuation profiles and canopy water budgets from precipitation and throughfall measurements. This system will be used for a forest hydrological study in the framework of the Dutch ACIFORN project, a research project on the effect of atmospheric deposition on Douglas fir vitality.

In the past, land consolidation projects in the Netherlands were aimed almost exclusively at increase of crop yields and farm income. Also the improvement of the water management system served agricultural purposes. Hydrological research, therefore, was directed to find optimal agrohydrological conditions. The results were translated into criteria for hydrological variables (like groundwater and surface water levels, discharge coefficients) and design rules for subsurface drainage systems. Initially the need to reduce excessive wetness was emphasized, later yield reduction due to water shortages in summer also became important. Lately the land consolidation projects have been renamed as “land development projects”. This is a result of recent developments in the rural areas, where aspects of nature conservation and outdoor recreation have become important items. Because water management measures in favour of one function often interfere with another, fixed design rules are no longer sufficient. The hydrological consequences for different interests have to be known beforehand. For the calculations of groundwater flow, analytical solutions are being replaced by numerical methods in order to cope with increasingly complex situations. Aspects of water quality are becoming more important. In addition to analyses of water samples, attention is paid to flow paths and stream velocities of groundwater, which give insight into the relation between quality and quantity. In this work, a close cooperation with agronomists and biologists has been established. A review is given of the hydrological models used for this purpose, at present and in the near future.

Observations in the Nabebuta and Kaioku districts show that the deep artesian water is not contaminated by the sea water, despite of the saline damage in the ground surface owing to the saline water percolation through the earth dam. The artesian heads in those areas are measured to be always lower than the sea level. These results suggest the existence of the impermeable layer between the aquifer and the sea water. Tidal changes in the water levels of four artesian wells are observed and are found the results corresponding with theoretically presented by the author under the assumption that the tidal effect on the artesian head is only due to the fluctuations in the loading weight upon the submarine aquifer. Some of the values which represent the characteristics of the aquifer are computed in using the analytical treatment from the observed results.

Intercepted rainfall may be evaporated during or after the rain event. Intercepted rain is generally determined as the difference between rainfall measurements outside and inside the forest. Such measurements are often used to discriminate between water storage and evaporation during rain as well. Two well-accepted methods underestimate water storage by a factor two as compared to direct observations. The underestimation of storage is compensated by an overestimation of evaporation during rain by a factor of three. The direct observations of water storage and evaporation appear to agree with previous direct observations. Thus, it is concluded that these observations are representative Also, our results based on methods using only rainfall measurements inside and outside the forest appear to agree with previous results, This would result in the conclusion that the common methods systematically underestimate water storage and overestimate evaporation during rain. Indeed, the systematic errors can be explained by the neglect of drainage before saturation. Water storage is better simulated assuming an exponential saturation of a larger storage capacity. A smaller evaporation can be simulated using an appropriate resistance to vapour transport. The observations in dense coniferous forest showed water storage to be the dominant process in rainfall interception, but this conclusion should not be generalized to other forests and climates. Direct observations of water storage and evaporation are recommended to build a realistic set of parameters for rainfall interception studies of the main vegetation types. (C) 1998 Elsevier Science B.V. All rights reserved.

In rapidly changing human-flood systems, dynamic models can assist with system thinking, policy-making, and response. Previous research has shown that flood memory is important for better responses during disasters. To date, socio-hydrological research has primarily focused on memory accumulation after flood events and the related dynamics and feedback mechanisms. Notably, the impact of risk information has not yet been considered in any modeling exercise. Accordingly, this study improved upon the socio-hydrological model (SHM) by incorporating the impact of risk information on collective memory and associated dynamics. Probable flood maps were used to assess the response of a floodplain community from the Lower Kelani River Basin, Sri Lanka, via two interview surveys conducted at a 6-month interval. The surveys were conducted under two categories: A—after distributing maps and conducting awareness sessions, and B—after showing and distributing flood maps. The results showed that the flood maps helped to improve the risk perception of floodplain communities. Of the two categories, the memory decay process was slower for Category A. Furthermore, the SHM application showed that flood damage in the study area could be reduced by 10–30% when flood maps were distributed, and awareness sessions were conducted at 1–5-yr intervals.

L'étude des activités hydrologiques menées au cours des cinquante dernières années dans les pays francophones de l'Afrique sub-saharienne apporte un précieux éclairage sur les difficultés rencontrées, les modes de collaboration adoptés et l'ampleur des défis à relever dans le domaine de l'eau à l'aube du troisième millénaire.Ceci est l'occasion de tracer les étapes marquantes de l'acquisition de la " connaissance hydrologique " depuis l'ère pionnière des années 50 jusqu'aux programmes scientifiques les plus récents faisant appel à des technologies avancées. Cette rétrospective permet également d'apprécier l'évolution des modes de partenariat entre acteurs scientifiques, techniques et économiques du Nord et du Sud.Ces travaux et recherches ainsi entrepris et développés montrent à la fois l'importance du savoir acquis et la nécessité de poursuivre les études en cours. Ils dressent aussi un constat encourageant quant à l'avenir des projets régionaux africains en hydrologie grâce au renforcement des relations scientifiques entre pays de la région., This article describes a study of hydrological research carried out in the French-speaking countries of sub-Saharan Africa over the past fifty years, by all the parties concerned.The work sheds useful light on the difficulties encountered, the types of co-operation adopted, and the scale of the challenge now facing the region in the matter of water resources, on the eve of the third millennium.The first stage in the acquisition of hydrological knowledge in the region was the pioneer period of the 1950s, when many different kinds of water demand were emerging very fast but hydrological information was almost nil. Hydrometric networks incorporating 1,500 instrument stations had to be rapidly set up for an overall survey of water resources. 200 representative or experimental catchments were equipped. The data obtained from the stations provided practical answers, meeting the operational needs of development, though in many cases the data acquired were used again, later on, for pure research purposes. The data gathering was a huge task, carried out on a range of different geographical scales. To achieve it, hydrologists had to develop appropriate methodologies for the region's tough climate and difficult field conditions; they also had to train highly motivated, seasoned hydrologists.During the sixties, the first hydrological monographs on the major river basins were completed,, rue Lafayette - research was conducted on regimes and ten-year flood peaks, and findings on the small catchments were collated. All this provided a first sketch of the region's main hydrological features.Two major upheavals marked the end of the 1960s: a long, disastrous drought and the information technology revolution.The scale of the hydropluviometric deficits recorded over several decades, amounting in some catchments to 30%-40%, led scientists to wonder how stable water resources really are and whether the notion of "normal" in hydrology or rainfall has any validity. The question was especially relevant because the design of all major African water engineering schemes completed around 1960-65 was necessarily influenced by the flow rates recorded in the previous, wet period. Changes in ground surface states and the environment in general, under the impact of climate change and increasing human activity respectively, made a more multidisciplinary approach to the hydrological cycle indispensable. Information technology also had a major impact, as the many numerical data gathered could at last be properly analysed and exploited. User-accessible reference databases were developed and processing software packages like Hydrom and Pluviom were widely distributed. It was now possible to model the relations between rainfall and discharges at a detailed scale; modelling improved steadily, first with the introduction of fine-mesh models, then of coupled surface water-groundwater models.As regards water engineering work, flood routing models were significantly improved for the Niger and Senegal rivers, and dam operation simulation models made spectacular strides. Of course, data processing greatly facilitated the use of statistical laws for everything to do with engineering hydrology.For several decades, metrology made little progress; but the instruments in use were robust and easy to use, and so well suited to local conditions. Not until the early 1980s was there significant technological progress in sensor technology; meanwhile civilian satellites made their debut and were used from the outset to facilitate hydrological data gathering, verification and transmission. Two applications illustrate this use locally. One is the Hydroniger project, involving eight countries bordering on the Niger and designed to produce an operational, real-time hydrological forecasting system on the river basin; the other is the Onchocerciasis Control Program, with WHO. In this program, discharge data in only slightly delayed time has made it possible to calculate the right dose of insecticide to add to infected rivers. Over the past ten or fifteen years, hydrological research has considerably extended its scope, to include spatialised hydrological parameters, soil/water/plant/atmosphere relations, soil erosion and conservation, geochemistry, hydrochemistry, etc. Meanwhile, sub-Saharan Africa has not been left out of the international organisations' programs involving operational or pure research hydrology, and it is making its contribution to the great challenges that face us with regard to water resources and management. Examples are the WMO WHYCOS project to establish permanent monitoring systems; the AOC-FRIEND program, a regional research project, which has been growing in strength; and the Hapex-Sahel experiment, designed to provide more information on the thermal and moisture characteristics of soil and vegetation, for integration into general atmospheric circulation models.Forms of collaboration among the partners involved in hydrology in this part of Africa have naturally changed over the course of fifty years. In the beginning, demand from local technical services set up a particular form of partnership with hydrology experts from the North. After independence, scientific and technical co-operation developed along with a policy for training management-level staff to build up national hydrology services. In many countries, however, the national services only gradually took full charge of their hydrometric networks, with technical assistance continuing for a long time. During the seventies and eighties, most countries acquired scientific or technical infrastructures that played host to hydrologists from the North for joint research programs and studies, with gradually increasing involvement by African water research scientists.After long years of work gathering, interpreting and applying data, the hydrological characteristics of this part of Africa have been established and the groundwork for a sound scientific partnership between Northern and Southern partners has been laid. Many of the region's water problems are linked to the difficulty of meeting constantly rising demand from fluctuating water resources; unrelenting effort is needed to resolve these problems.In this regard, there are promising signs for the new millennium: the growing community of African hydrologists is increasingly active in major international programs; links have been forged among those involved in Africa's various regional programs; and there are now thriving scientific associations like the Association of African Hydrologists.

Processes controlling groundwater recharge have been a topic of pursuit in the hydrological research community. The groundwater recharge in hard-rock aquifers is significantly impacted by rainfall patterns, aquifer characteristics, weathering/soil conditions, topography, land use, and land cover. Analysis of the recharge process in tropical semi-arid hard-rock aquifer regions of southern India is crucial due to several factors, including (a) a heavily tailed monsoon system prevailing in the region, which is characterized by very few episodic storm events; (b) heterogeneity of aquifers in terms of fractures; and (c) the presence of several man-made irrigation lakes/tanks along with the drainage network. This study uses a lumped unconfined aquifer model to estimate the groundwater recharge for nine locations in Gundlupet taluk and 150 locations in Berambadi Experimental Watershed (EWS) in the south Indian state of Karnataka. Analysis of estimated recharge factors identifies 30 high-episodic recharge events out of 292 observations (around 10%) in Gundlupet taluk and 80 out of 150 locations in 2017 in Berambadi EWS. Partial information correlation (PIC) analysis is used to select the significant predictors out of potential predictors based on rainfall intensity distribution and climatological indices. PIC analysis reveals that the number of rainfall events with 15–30 mm daily rainfall intensity are most significant for normal recharge events in Gundlupet taluk and Berambadi EWS. The combined information on daily rainfall distribution, daily rainfall events of 20–40 mm, and the number of La Niña months in a particular year can explain the variability of high-episodic recharge events in Gundlupet taluk. These high-intensity rainfall events can be potential sources of alternate recharge pathways resulting in faster indirect recharge, which dominates the diffused recharge and results in high-episodic recharge events. Rainfall intensity distribution and climatological indices contain the potential information required to disaggregate normal and high-episodic recharge factors for future rainfall projections, which is useful for future groundwater level projections.

The increasing interest in hydrological studies in the United Arab Emirates (UAE) has resulted in the publication of several papers on hydrology and its broad use for addressing contemporaneous challenges confronting humans and the environment in the region. However, for several reasons, these efforts have remained invisible and unrecognized. This paper has reviewed the literature on hydrological research in the UAE to provide a comprehensive source of information for researchers, practitioners, policymakers, and other stakeholders. The documented studies were carefully selected, relying on a bibliometric analysis methodology of five phases to specify the boundary of the study area, adopt the primary keywords for the search, evaluate the obtained papers, exclude the non-conforming ones, and classify the final results into four distinguished topics—namely, rainfall analysis, urban growth and flood hazards, cloud seeding and changing climate, and groundwater situation and utilization. The evaluation process considered assessing the papers’ relevancy, authenticity, and coverage of the main issues of interest. In all, a total of 50 published papers were identified based on the specified criteria and reviewed. The main findings were first that the amount of rainfall over the UAE has been declining in the last decade, and this trend is expected to continue, although intensities are rising, suggesting shorter duration events. Secondly, the extensive urban growth in the country has resulted in increasing incidences of urban floods and declining groundwater recharge. Both of these are to be expected as consequences of the increased imperviousness from urbanization and the higher intensities from shorter-duration rainfall events. Thirdly, although the cloud-seeding program has proved to be successful in increasing precipitation amounts, the impact of this on flooding due to more extreme rainfall intensities and on air quality remains worrisome. Finally, groundwater analyses have shown that it is still the main freshwater resource in the country, but its long-term sustainability and quality are being threatened by the declining recharge. This calls for a national policy for groundwater management in the UAE to tackle the challenges associated with the increasing demand for water in all sectors of the economy. The study recommended addressing the gap in the hydrological literature of the UAE, specifically in the field of big meteorological data analysis, the socioeconomic impacts of urban floods, the impacts of climate change in urbanized regions, and the possibility of using alternative resources to recharge groundwater as part of sustainable water management.

Soil moisture (SM) and temperature (ST) are critical factors in forest eco-hydrological research. In this study, we investigated the inter- and intra-annual changes in SM and ST profiles in a mixed Mediterranean maquis forest stand together with soil and meteorological parameters. Hourly data from three field measurements points at four depths (−5, −20, −40 and −70 cm) for 6 years were interpolated using the kriging method to produce annual SM and ST profiles. The results indicate that air temperature highly affects the upper 5 cm of the mineral soil. In general, it increases with depth in winter at an average rate of 0.036 °C/cm and decreases in summer (0.035 °C/cm), presenting higher values compared to air temperature from April to August and lower ones during the rest of the period. Precipitation is the main factor driving SM variations up to a superficial soil depth of 40 cm. The upper soil layer (0–40 cm) infiltrates water faster and presents high SM variability, especially in monthly and seasonal (year to year) time steps. The maquis forest stands are likely to be strongly affected by climate change, therefore the results of this study could be useful in hydrological and climate change studies focused on maquis vegetation water management.

Extensive deforestation in tropical regions may significantly influence the hydrological cycle. However, subsurface runoff processes in thick soil layers in humid tropical forests are poorly understood; thus, the impact of land-use changes in such regions remains unclear. To understand runoff generation mechanisms in the humid tropics, we monitored groundwater and soil moisture dynamics in a forested hillslope in Sumatra, Indonesia. We also conducted field and laboratory experiments to determine soil hydraulic characteristics and used the results to simulate vertical infiltration and groundwater recharge. Although the soil is categorized as silty clay loam, the high infiltrability and high water retention capacity of the soil enabled infiltration during storm events and recharge to groundwater. Within the 4–5 m thick soil layer at the foot of the hillslope, the shallow groundwater table quickly responded to rainfall and did not drop below a depth of 2–3 m, possibly due to continuous flow contributions from the upslope. Overall, this study demonstrates the importance of subsurface flow and vertical infiltration in thick soil layers in humid tropical regions.

Simulating streamflow under both high-and low-flows is required for versatile eco-hydrological modeling. Typical streamflow simulators require hydrological data such as river geometry and observed river discharge/water level as upstream/downstream boundary conditions. However, these are not always available in data-sparse regions. Furthermore, because of the potential inaccuracy of digital elevation model (DEM) data around water surfaces, this data has not generally been utilized in streamflow simulations. Therefore, this study explores the potential applicability of DEM data to extract river cross-sections, focusing on the upstream Hiikawa River, Japan. A 1-D streamflow simulation was performed using river cross-sections extracted from a 5 m LiDAR DEM and the observed dam discharge from 2018 to 2020 as the upstream boundary condition. The simulated water depths with Manning’s roughness coefficients of 0.03 to 0.05 m–1/3 s reproduce the observation results with Nash-Sutcliffe coefficients of 0.91–0.97 for the whole period and 0.60–0.97 for a flood event. The accurate results for both low and high flows were considered to reflect the reasonable representations of the river cross-section. Finally, the velocity-based suitability index for Ayu (P. altivelis) was evaluated. We demonstrate applicability and several possible limitations of DEM data for eco-hydrological modeling of data-scarce rivers.