Water is the essential resource of the 21st century where innovative water management strategies are needed to improve water security. This paper examines three case studies that exemplify the global water crisis, situated in rapidly urbanizing watersheds: Nairobi River Basin, Kenya; Citarum River Basin, Indonesia; and Addis Ababa River Basin, Ethiopia. Each of these watersheds are implementing large-scale water management strategies inclusive of local communities and regional governments to address water quality and waste management issues. The hydrosocial cycle (Linton, 2010) provides a framework to investigate the social, technical and physical aspects of water flows. Using the hydrosocial cycle as an organizing framework, these watersheds are examined to highlight how water security underpins water justice. The issues of gender and inequity are often overlooked in larger policy, development, and infrastructure discussions where technical requirements, restoration management, and engineering solutions obscure power inequities. Projects are compared to assess the implementation of the hydrosocial cycle through a discussion of social power and structure, technology and infrastructure, and the materiality of water in each location. This comparison reveals a dependence on large-scale technical projects with limited community engagement, and a need for science-based river restoration management. Recommendations are provided to improve and address holistic water management.

In rural north-western China, the tension between economic growth and ecological crises demonstrates the limitations of dominant top-down approaches to water management. In the 1990s, the Chinese government adopted the Integrated Water Resources Management (IWRM) approach to combat the degradation of water and ecological systems throughout its rural regions. While the approach has had some success at reducing desertification, water shortage, and ecological deterioration, there are important limitations and obstacles that continue to impede optimum outcomes in water management. As the current IWRM approach is instituted through a top-down centralized bureaucratic structure, it often fails to address the socio-political context in which water management is embedded and therefore lacks a complete treatment of how power is embedded in the bureaucracy and how it articulates through economic growth imperatives set by the Chinese state. The approach has relied on infrastructure heavy and technocratic solutions to govern water demand, which has worked to undermine the focus on integration and public participation. Finally, the historical process through which water management mechanisms have been instituted are fraught with bureaucratic fragmentation and processes of centralization that work against some of its primary goals such as reducing uncertainty and risk in water management systems. This article reveals the historical, social, political, and economic processes behind these shortcomings in water management in rural north-western China by focusing on the limitations of a top-down approach that rely on infrastructure, technology, and quantification, and thereby advances a more holistic, socio-political perspective for water management that considers the state-society dynamics inherent in water governance in rural China.

In semi-arid regions, air temperatures have increased in the last decades more than in many other parts of the world. Mongolia has an arid/semi-arid climate and much of the population are herders whose livelihoods depend upon limited water resources that fluctuate with a variable climate. Herders were surveyed to identify their observations of changes in climate extremes for two soums of central Mongolia, Ikh-Tamir in the forest steppe north of the Khangai Mountains and Jinst in the desert steppe south of the mountains. The herders’ indigenous knowledge of changes in climate extremes mostly aligned with the station-based analyses of change. Temperatures were warming with more warm days and nights at all stations. There were fewer cool days and nights observed at the mountain stations both in the summer and winter, yet more cool days and nights were observed in the winter at the desert steppe station. The number of summer days is increasing while the number of frost days is decreasing at all stations. The results of this study support further use of local knowledge and meteorological observations to provide more holistic analysis of climate change in different regions of the world.

Anti-filtration recharge wells are commonly installed in river channels and irrigation canals on the Shandong Peninsula, China, and can be used as an important recharge facility for underground reservoirs. However, during recharge, as the running time increases, the recharge capacity gradually decreases. This study was undertaken to develop a new recharge well and mitigate this deficiency. A round empty core infiltration and anti-filtration recharge well and laboratory recharge test equipment were developed. Subsequently, 1:25 models of the recharge pond, a round empty core recharge wellhead, and an artificial recharge well were prepared. Using equal recharge levels and ambient groundwater levels, laboratory steady-flow recharge tests on the existing anti-filtration recharge well, the new round empty core infiltration and anti-filtration recharge well, and an artificial recharge well were carried out. Experimental data on the measured groundwater table and single-well recharge quantity were also collected and analyzed. The results showed that compared with the existing anti-filtration recharge well, the new round empty core infiltration and anti-filtration recharge well had stronger anti-deposition and anti-scouring properties, and the single-well recharge quantity increased by 403%. With an increase in the number of recharge tests, the single-well recharge quantity gradually decreased and tended to stabilize as a whole.

To make sense of physical clogging during Yellow River water spreading in the strong leakage zone of the Yufuhe River, a laboratory sand column experiment was undertaken and the heterogeneous sand gravel with a uniformity coefficient of 25.2 from the Yufuhe River was used as an infiltration medium. Under either the condition of raw sand or washed sand, physical clogging tests were conducted with constant hydraulic heads of 10 cm and 30 cm and inflow suspension concentrations of 200 mg/L, 500 mg/L, and 1000 mg/L. The fine particles in the suspension and in the raw sand were considered exogenous and endogenous particles, respectively. Rapid clogging was observed in the porous medium when the inflow concentrations of the exogenous particles were high, and increased hydraulic head led to serious clogging. This result indicated that the Yufuhe River has a strong recharge capability with respect to clogging. The analysis of particle content shows that endogenous fine particles (diameter 1–10 mm and 50–74 mm) had less mobility and generally accumulated in the sand column, whereas particles with diameter 10–50 mm had greater mobility in the sand column. And the distribution of exogenous fine particles size after movement is relatively uniform in the sand column. Field observations indicated that the filtration effect of the aquifers have greatly improved the water quality of recharge water in the strong leakage zone of the Yufuhe River, and test data of turbidity also verified the results of the sand column experiments.

The snowpack is changing across the globe, as the climate warms and changes. We used daily snow water equivalent (SWE) niveograph (time series of SWE) data from 458 snow telemetry (SNOTEL) stations for the period 1982 through 2012. Nineteen indices based on amount, timing, time length, and rates were used to describe the annual temporal evolution in SWE accumulation and ablation. The trends in these annual indices were computed over the time period for each station using the Theil-Sen slope. These trends were then clustered into four groups to determine the spatial pattern of SWE trends. Temperature and precipitation data were extracted from the PRISM data set, due to the shorter time period of temperature measurement at the SNOTEL stations.

Results show that SNOTEL stations can be clustered in four clusters according to the observed trends in snow indices. Cluster 1 stations are mostly located in the Eastern- and South-eastern most parts of the study area and they exhibit a generalized decrease in the indices related with peak SWE and snow accumulation. Those stations recorded a negative trend in precipitation and an increase in temperature. Cluster 4 that is mostly restricted to the North and North-west of the study area shows an almost opposite pattern to cluster 1, due to months with positive trends and a more moderate increase of temperature. Stations grouped in clusters 2 and 3 appear mixed with clusters 1 and 4, in general they show very little trends in the snow indices.

Debris flow is one of the most destructive water related mass movements that affects the development of mountain terrains. A reliable assessment of debris flow susceptibility requires adequate data, but in most developing countries like India, there is a dearth of such extensive scientific records. This study presents a novel approach for assessing debris flow using the analytical network process (ANP) in data insufficient regions. A stretch of hill road between Kumburvayal and Vadakaunchi along the Kodaikkanal-Palani Traffic Corridor (M171) was considered for this study. Five significant factors including the nature of slope forming materials, hydraulic conductivity, slope, vegetation, and drainage density were identified from intense field surveys and inspections in order to assess the susceptibility of the terrain to debris flow. This model endorsed the interdependencies between the selected factors. The resulting debris flow susceptibility map delineated regions highly prone to debris flow occurrences, which constituted nearly 23% of the selected road stretch.

An integrated study of biostratigraphy, microfacies, and stable carbon isotope stratigraphy was carried out on the late Famennian–early Asselian carbonates of the Long’an section in Guangxi, South China. Stable carbon isotope studies in the Long’an section have revealed four major positive shifts of δ¹³C values in the Carboniferous strata in South China. The first shift occurred in the Siphonodella dasaibaensia zone in the Tournaisian, with an amplitude of 4.19‰. The second shift occurred near the Visean/Serpukhovian boundary, with an amplitude of 2.63‰. The third shift occurred in the Serpukhovian, with an amplitude of 3.95‰. The fourth shift occurred in the Kasimovian, with an amplitude of 3.69‰. Furthermore, there were several brief positive δ¹³C shifts during the late Famennian to early Tournaisian. All of these shifts can be well correlated globally, and each corresponds to sea-level regressions in South China and Euro-America, indicating increases in ocean primary productivity and global cooling events. Chronologically, the four major positive excursions of δ¹³C, together with several brief positive δ¹³C shifts that were observed during the late Famennian to the early Tournaisian, correspond to the well-accepted Glacial I, II, and III events.

Terrace and check dam construction has substantially changed land surface morphology, which in turn affects modern surface processes. Digital elevation models (DEMs) provide an effective way to quantitatively analyze surface morphology and processes. However, existing DEMs lack sufficient ability to express artificial terrain. Based on 1:10000 topographic maps of the Zhifanggou watershed, a series of artificial terrain DEMs for the study site were constructed by both field investigation and remote sensing images from 1938 to 2010. Digital terrain analysis was used to quantitatively assess the influence of terrace and check dam construction on the watershed terrain. The results showed that the artificial terrain DEM could capture the spatial distribution patterns of terraces and dam lands and improved the ability of DEM to express terrain. The construction of terraces and check dams clearly changed the surface elevation. The average elevation change of each terrace mainly ranged between –1.5 and 1.5 m, while the annual average deposition height of the dam lands was 9.16 cm. The average slope, slope length, and slope length and steepness factor of the watershed decreased with the effect of the artificial terrain on the surface, and their averages decreased by 0.65°, 6.75 m, and 0.83, respectively, from 1938 to 2010. Although the construction of terraces reduced their surface slope to nearly 0°, the slope of terrace embankments rapidly increased, to more than 45°, which may lead to gravitational erosion and potential terrace damage. Terracing reduced the slope length in both the terrace distribution area and downslope of the terraces. Check dam deposition reduced the slope and slope length of the channel. This study contributes to a better understanding of the topographic change rules after terrace and check dam construction, and aids in elucidating the mechanisms of soil erosion process influenced by artificial topography.

GPS-based surface drifters were used to investigate the surface currents in Daya Bay and along the eastern Guangdong coast in China. Surface current vectors were measured based on the GPS location and corresponding time information sent by drifters through the mobile phone network. The analysis of data from 120 drifters, deployed in late spring 2018 in the case-study region, shows that the drifters are generally capable of capturing the surface (tidal and residual) currents. The drifter trajectories suggest an anticlockwise surface current inside Daya Bay and a north-eastward current along the eastern Guangdong coast, where the coastal current along the eastern Guangdong coast is faster than that inside Daya Bay. The surface currents in the investigated region follow an irregular semidiurnal cycle due to the influence of the tidal current, while the currents inside Daya Bay are strongly affected by the topography. According to the harmonic analysis, an irregular semidiurnal type of tidal current is evident at a study grid inside Daya Bay, with an Eulerian residual current speed of 9.0 cm/s and a direction of 276°. The Lagrangian residual current outside Daya Bay moves north-eastward with a mean speed of 22 cm/s along the eastern Guangdong coast, while the current inside Daya Bay moves northward to the bay head with a mean speed of about 8.0 cm/s, which agrees well with the one reported in other literatures.

In a typical Case-2 coastal water environment (here, the Pearl River Estuary (PRE), China), chromophoric dissolved organic matter (CDOM) and suspended particulates dominate the water optical properties, and CDOM fluorescence contributes considerably to surface water reflectance. In this paper, an ultraviolet (UV) to visible scheme to retrieve CDOM absorption (a_g) is developed based on a set of in situ observations. First, the CDOM UV absorption and spectral slope (S_g) are derived directly from the visible remote sensing reflectance; then the S_g is extrapolated to obtain the spectrum from UV to visible spectral range. This algorithm performs well, with an overall mean absolute percent difference (MAPD) of ~30%, ~5% and ~6% for the estimation of a_g in 250–450 nm, S_g over 250–400 nm, and 250–700 nm, respectively. The effectiveness and stability of the algorithm is further demonstrated in capturing the distribution pattern of CDOM absorption in the PRE from satellite ocean color imagery with multiple spatial and spectral resolution, namely: the Visible Infrared Imaging Radiometer Suite (VIIRS) (750 m/Multispectral), the Ocean and Land Color Instrument (OLCI) (300 m/Multispectral), the Hyperspectral Imager for the Coastal Ocean (HICO) (100 m/Hyperspectral), and the Landsat 8 Operational Land Imager (OLI) (30 m/Multispectral). The UV to visible scheme can benefit the CDOM absorption estimation in two aspects: 1) it is free from the disturbance of suspended matter; 2) it avoids uncertainties caused by the low signal-to-noise ratio (SNR) of a_g measurements in the visible range. The algorithm is effective in revealing multiple scales of variation of CDOM absorption from ocean color observations.

Building damage assessment is of great significance to disaster monitoring. Polarimetric Synthetic Aperture Radar (SAR) can record the polarization scattering measurement matrix of ground objects and obtain more abundant ground object information, meaning that they can be used for assessing damage to buildings. In this paper, a new approach is proposed to assess building damage using the Touzi incoherent decomposition and SAR-based characteristics of buildings before and after damage. The March 11th, 2011 earthquake that struck the coast of north-east Japan serves as the demonstration of the technique using quad-polarimetric ALOS PALSAR data acquired before and after the disaster. The analysis shows that after the buildings are damaged, there is a clear decrease in the {\alpha }_{\mathrm{s}\mathrm{1}} (the dominant scattering-type magnitude) components and the degree of this reduction corresponds to the degree of building damage. This means that the {\alpha }_{\mathrm{s}\mathrm{1}} components obtained by Touzi decomposition can effectively reflect the degree of building damage. On this basis, a model based on Touzi decomposition was established to evaluate the degree of damage to buildings, and the accuracy of the model was validated using high-resolution optical data acquired before and after the earthquake. The experimental results show that Touzi decomposition can be effectively used for damage assessment mapping in built-up areas.

Qinghai Province is one of the four largest pastoral regions in China. Timely monitoring of grass growth and accurate estimation of grass yields are essential for its ecological protection and sustainable development. To estimate grass yields in Qinghai, we used the normalized difference vegetation index (NDVI) time-series data derived from the Moderate-resolution Imaging Spectroradiometer (MODIS) and a pre-existing grassland type map. We developed five estimation approaches to quantify the overall accuracy by combining four data pre-processing techniques (original, Savitzky-Golay (SG), Asymmetry Gaussian (AG) and Double Logistic (DL)), three metrics derived from NDVI time series (VI_max, VI_season and VI_mean) and four fitting functions (linear, second-degree polynomial, power function, and exponential function). The five approaches were investigated in terms of overall accuracy based on 556 ground survey samples in 2016. After assessment and evaluation, we applied the best estimation model in each approach to map the fresh grass yields over the entire Qinghai Province in 2016. Results indicated that: 1) For sample estimation, the cross-validated overall accuracies increased with the increasing flexibility in the chosen fitting variables, and the best estimation accuracy was obtained by the so called “fully flexible model” with R² of 0.57 and RMSE of 1140 kg/ha. 2) Exponential models generally outperformed linear and power models. 3) Although overall similar, strong local discrepancies were identified between the grass yield maps derived from the five approaches. In particular, the two most flexible modeling approaches were too sensitive to errors in the pre-existing grassland type map. This led to locally strong overestimations in the modeled grass yields.

Earth observation technologies are important for obtaining geospatial information on the Earth’s surface and are used widely in many disciplines, such as resource surveying, environmental monitoring, and evolutionary studies. However, it is a challenge for existing Earth observation platforms to acquire this type of data rapidly on a global scale due to limitations in orbital altitude and field of view; thus development of an advanced platform for Earth observation is desirable. As a natural satellite of the Earth, placement of various sensors on the Moon could possibly facilitate comprehensive, continuous, and long-term observations of the Earth. This is a relatively new concept and the study is still at the preliminary stage with no actual Moon-based Earth observation data available at this time. To understand the characteristics of Moon-based microwave radiation, several physical factors that potentially influence microwave radiation imaging, e.g., time zone correction, relative movement of the Earth-Moon, atmospheric radiative transfer, and the effect of the ionosphere, were examined. Based on comprehensive analysis of these factors, the Moon-based microwave brightness temperature images were simulated using spaceborne temperature data. The results show that time zone correction ensures that the simulation images may be obtained at Coordinated Universal Time (UTC) and that the relative movement of the Earth-Moon affects the positions of the nadir and Moon-based imaging. The effect of the atmosphere on Moon-based observation is dependent on various parameters, such as atmospheric pressure, temperature, humidity, water vapor, carbon dioxide, oxygen, the viewing zenith angle and microwave frequency. These factors have an effect on atmospheric transmittance and propagation of upward and downward radiation. When microwaves propagate through the ionosphere, the attenuation is related to frequency and viewing zenith angle. Based on initial studies, the simulation results suggest Moon-based microwave radiation imaging is realistic and viable.

Forest fires, whether caused naturally or by human activity can have disastrous effects on the environment. Turkey, located in the Mediterranean climate zone, experiences hundreds of forest fires every year. Over the past two decades, these fires have destroyed approximately 308000 ha of forest area, threatening the sustainability of its ecosystem. This study analyzes the forest fire that occurred in the Menderes region of Izmir on July 1, 2017, by using pre- and post-fire Sentinel 2 (10 m and 20 m) and Landsat 8 (30 m) satellite images, MODIS and VIIRS fire radiative power (FRP) data (1000 m and 375 m, respectively), and reference data obtained from a field study. Hence, image processing techniques integrated with the Geographic Information System (GIS) database were applied to a satellite image data set to monitor, analyze, and map the effects of the forest fire. The results show that the land surface temperature (LST) of the burned forest area increased from 1 to 11°C. A high correlation (R= 0.81) between LST and burn severity was also determined. The burned areas were calculated using two different classification methods, and their accuracy was compared with the reference data. According to the accuracy assessment, the Sentinel (10 m) image classification gave the best result (96.43% for Maximum Likelihood, and 99.56% for Support Vector Machine). The relationship between topographical/forest parameters, burn severity and disturbance index was evaluated for spatial pattern distribution. According to the results, the areas having canopy closure between 71%–100% and slope above 35% had the highest burn incidence. As a final step, a spatial correlation analysis was performed to evaluate the effectiveness of MODIS and VIIRS FRP data in the post-fire analysis. A high correlation was found between FRP-slope, and FRP-burn severity (0.96 and 0.88, respectively).

Grasslands play a key role in both carbon and water cycles. In semi-arid and arid grassland areas, the frequency and intensity of droughts are increasing. However, the influence of a drought on grassland carbon cycling is still unclear. In this paper, the relationship between drought and grassland carbon cycling is described from the perspective of drought intensity, frequency, duration, and timing. Based on a large amount of literature, we determined that drought is one of the most prominent threats to grassland carbon cycling, although the impacts of different drought conditions are uncertain. The effects of a drought on grassland carbon cycling are more or less altered by drought-induced disturbances, whether individually or in combination. Additionally, a new conceptual model is proposed to better explain the mechanism of droughts on grassland carbon cycling. At present, evaluations of the effects of droughts on grassland carbon cycling are mainly qualitative. A data fusion model is indispensable for evaluating the fate of carbon cycling in a sustainable grassland system facing global change. In the future, multi-source data and models, based on the development of single and multiple disturbance experiments at the ecosystem level, can be utilized to systematically evaluate drought impacts on grassland carbon cycling at different timescales. Furthermore, more advanced models should be developed to address extreme drought events and their consequences on energy, water, and carbon cycling.

Knowledge of historical changes in moisture within semi-arid and arid regions is the basis of climatic change predictions and strategies in response to long-term drought. In this study, a multiproxy peat record with high-resolution from Sichanghu in the northern Tianshan was used to document the changes in vegetation and climate over the past 450 years in the arid Central Asia. The pollen, grain size, and loss on ignition (LOI) records indicate that the productivity of local peat began to increase at ~1730 AD. The vegetation in the Sichanghu area experienced several transitions, from temperate desert to dense desert, marsh meadow, and steppe desert vegetation. The climate in the study area was extremely dry during the early stages of the Little Ice Age (LIA) (before 1730 AD) and relatively wet during the late stages (1730–1880 AD). The inferred changes in the moisture conditions of the Sichanghu peatland since the LIA may have been controlled by the extent of Arctic sea ice, the North Atlantic Oscillation, and the Siberian High via the connections of large-scale atmospheric circulations such as the Westerlies.