The Indus basin heavily depends on its upstream mountainous part for the downstream supply of water while downstream demands are high. Since downstream demands will likely continue to increase, ...accurate hydrological projections for the future supply are important. We use an ensemble of statistically downscaled CMIP5 General Circulation Model outputs for RCP4.5 and RCP8.5 to force a cryospheric-hydrological model and generate transient hydrological projections for the entire 21st century for the upper Indus basin. Three methodological advances are introduced: (i) A new precipitation dataset that corrects for the underestimation of high-altitude precipitation is used. (ii) The model is calibrated using data on river runoff, snow cover and geodetic glacier mass balance. (iii) An advanced statistical downscaling technique is used that accounts for changes in precipitation extremes. The analysis of the results focuses on changes in sources of runoff, seasonality and hydrological extremes. We conclude that the future of the upper Indus basin's water availability is highly uncertain in the long run, mainly due to the large spread in the future precipitation projections. Despite large uncertainties in the future climate and long-term water availability, basin-wide patterns and trends of seasonal shifts in water availability are consistent across climate change scenarios. Most prominent is the attenuation of the annual hydrograph and shift from summer peak flow towards the other seasons for most ensemble members. In addition there are distinct spatial patterns in the response that relate to monsoon influence and the importance of meltwater. Analysis of future hydrological extremes reveals that increases in intensity and frequency of extreme discharges are very likely for most of the upper Indus basin and most ensemble members.
Glaciers in the high mountains of Asia (HMA) make a substantial contribution to the water supply of millions of people, and they are retreating and losing mass as a result of anthropogenic climate ...change at similar rates to those seen elsewhere. In the Paris Agreement of 2015, 195 nations agreed on the aspiration to limit the level of global temperature rise to 1.5 degrees Celsius ( °C) above pre-industrial levels. However, it is not known what an increase of 1.5 °C would mean for the glaciers in HMA. Here we show that a global temperature rise of 1.5 °C will lead to a warming of 2.1 ± 0.1 °C in HMA, and that 64 ± 7 per cent of the present-day ice mass stored in the HMA glaciers will remain by the end of the century. The 1.5 °C goal is extremely ambitious and is projected by only a small number of climate models of the conservative IPCC's Representative Concentration Pathway (RCP)2.6 ensemble. Projections for RCP4.5, RCP6.0 and RCP8.5 reveal that much of the glacier ice is likely to disappear, with projected mass losses of 49 ± 7 per cent, 51 ± 6 per cent and 64 ± 5 per cent, respectively, by the end of the century; these projections have potentially serious consequences for regional water management and mountain communities.
Continually improving and affordable wastewater management provides opportunities for both
pollution reduction and clean water supply augmentation, while simultaneously promoting
sustainable ...development and supporting the transition to a circular economy. This study aims to
provide the first comprehensive and consistent global outlook on the state of domestic and
manufacturing wastewater production, collection, treatment and reuse. We use a data-driven approach,
collating, cross-examining and standardising country-level wastewater data from online data
resources. Where unavailable, data are estimated using multiple linear regression. Country-level
wastewater data are subsequently downscaled and validated at 5 arcmin
(∼10 km) resolution. This study estimates global wastewater production at 359.4×109 m3 yr−1, of which 63 % (225.6×109 m3 yr−1) is
collected and 52 % (188.1×109 m3 yr−1) is treated. By extension, we
estimate that 48 % of global wastewater production is released to the environment untreated,
which is substantially lower than previous estimates of ∼80 %. An estimated 40.7×109 m3 yr−1 of treated wastewater is intentionally reused. Substantial
differences in per capita wastewater production, collection and treatment are observed across
different geographic regions and by level of economic development. For example, just over 16 %
of the global population in high-income countries produces 41 % of global wastewater. Treated-wastewater reuse is particularly substantial in the Middle East and North Africa (15 %) and
western Europe (16 %), while comprising just 5.8 % and 5.7 % of the global population,
respectively. Our database serves as a reference for understanding the global wastewater status
and for identifying hotspots where untreated wastewater is released to the environment, which are
found particularly in South and Southeast Asia. Importantly, our results also serve as a baseline
for evaluating progress towards many policy goals that are both directly and indirectly connected
to wastewater management. Our spatially explicit results available at 5 arcmin
resolution are well suited for supporting more detailed hydrological analyses such as water
quality modelling and large-scale water resource assessments and can be accessed at
https://doi.org/10.1594/PANGAEA.918731 (Jones
et al., 2020).
Climate change poses a significant threat to global biodiversity, but freshwater fishes have been largely ignored in climate change assessments. Here, we assess threats of future flow and water ...temperature extremes to ~11,500 riverine fish species. In a 3.2 °C warmer world (no further emission cuts after current governments' pledges for 2030), 36% of the species have over half of their present-day geographic range exposed to climatic extremes beyond current levels. Threats are largest in tropical and sub-arid regions and increases in maximum water temperature are more threatening than changes in flow extremes. In comparison, 9% of the species are projected to have more than half of their present-day geographic range threatened in a 2 °C warmer world, which further reduces to 4% of the species if warming is limited to 1.5 °C. Our results highlight the need to intensify (inter)national commitments to limit global warming if freshwater biodiversity is to be safeguarded.
Groundwater is the world's largest freshwater resource and is critically important for irrigation, and hence for global food security
. Already, unsustainable groundwater pumping exceeds recharge ...from precipitation and rivers
, leading to substantial drops in the levels of groundwater and losses of groundwater from its storage, especially in intensively irrigated regions
. When groundwater levels drop, discharges from groundwater to streams decline, reverse in direction or even stop completely, thereby decreasing streamflow, with potentially devastating effects on aquatic ecosystems. Here we link declines in the levels of groundwater that result from groundwater pumping to decreases in streamflow globally, and estimate where and when environmentally critical streamflows-which are required to maintain healthy ecosystems-will no longer be sustained. We estimate that, by 2050, environmental flow limits will be reached for approximately 42 to 79 per cent of the watersheds in which there is groundwater pumping worldwide, and that this will generally occur before substantial losses in groundwater storage are experienced. Only a small decline in groundwater level is needed to affect streamflow, making our estimates uncertain for streams near a transition to reversed groundwater discharge. However, for many areas, groundwater pumping rates are high and environmental flow limits are known to be severely exceeded. Compared to surface-water use, the effects of groundwater pumping are markedly delayed. Our results thus reveal the current and future environmental legacy of groundwater use.
Global depletion of groundwater resources Wada, Yoshihide; van Beek, Ludovicus P. H.; van Kempen, Cheryl M. ...
Geophysical research letters,
October 2010, Letnik:
37, Številka:
20
Journal Article
Recenzirano
Odprti dostop
In regions with frequent water stress and large aquifer systems groundwater is often used as an additional water source. If groundwater ion exceeds the natural groundwater recharge for extensive ...areas and long times, overexploitation or persistent groundwater depletion occurs. Here we provide a global overview of groundwater depletion (here defined as ion in excess of recharge) by assessing groundwater recharge with a global hydrological model and subtracting estimates of groundwater ion. Restricting our analysis to sub‐humid to arid areas we estimate the total global groundwater depletion to have increased from 126 (±32) km3 a−1 in 1960 to 283 (±40) km3 a−1 in 2000. The latter equals 39 (±10)% of the global yearly groundwater ion, 2 (±0.6)% of the global yearly groundwater recharge, 0.8 (±0.1)% of the global yearly continental runoff and 0.4 (±0.06)% of the global yearly evaporation, contributing a considerable amount of 0.8 (±0.1) mm a−1 to current sea‐level rise.
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