Coral
reefs are the most diverse coastal ecosystems on earth and of disproportionate
ecological, economic and food security importance to the Asia-Pacific region
which has an inordinate proportion of the world’s healthy coral reefs. Coral diversity is highest in the Asia-Pacific
region.
The death of
reef-forming corals undermines resilience of coastal communities, and can lead
to the collapse of important coastal ecosystems.
One
third of reef- building corals in the region are threatened.
Loss
of habitat quality, heavy damage to entire reefs are major
threats in the region. In the case of El Niño event in 1998, 16 per cent of
the world’s coral reefs and 50 per cent of those in the Indian Ocean were
destroyed
Increase
in sea temperature and ocean acidification have been
projected as major drivers of change along coastal environments which may lead
to decline in coral reefs.
Increasing
outbreaks of crown of thorns starfish, a native predator that has boom
bust cycles linked to environmental pollution from farm lined estuaries
affected The Great Barrier Reef.
Coral
bleaching events are also increasingly devastating to the northern two thirds of
the reef over the last few years where coral-algae associations are disrupted
by high sea temperature. Habitats and
communities in the Great Barrier Reef ranged from poor to worsening at the end
of 2015, although some species like green turtle populations improved.
Among
the most serious emerging threats to coral reefs are coral diseases, which have
devastated coral populations throughout the Caribbean since the 1980s and
accompanied the mass coral bleaching there in 2005 and 2006. Over 90 per cent
of the main reef forming corals in the Caribbean have now died due to coral
disease with the severity of disease outbreaks commonly correlated with corals
stressed by bleaching. Coral diseases
are also being observed more frequently on Indo-Pacific reefs in heretofore
unrecorded places such the Great Barrier Reef, areas of Marovo Lagoon in the
Solomon Islands and the Northwestern Hawaiian Islands. The outbreaks seem to be
related to bacterial infections and other introduced disease organisms,
increasing pollution, human disturbance and increasing sea temperature, all of
which have put reef-forming corals at serious risk.
Marine ecosystems, from coastal to deep sea, now show the influence of human actions, with coastal marine ecosystems showing both large historical losses of extent and condition as well as rapid ongoing declines (established but incomplete) {2.2.5.2.1, 2.2.7.15}
Direct exploitation of fish and seafood has the largest relative impact in the oceans (well established) {2.2.6.2}.
The direct driver with the second highest impact on the oceans is the many changes in the uses of the sea and coast land (well established) {2.2.6.2} (See Summary of Observed Changes)
Distribution Of Changes In The Global Ocean
Source: Halpern
(B. S., Walbridge, S., Selkoe, K. A., Kappel, C. V., Micheli, F.,
D’Agrosa, C., … Watson, R. (2008). A Global Map of Human Impact on
Marine Ecosystems. Science, 319(5865), 948–952.doi:10.1126/science.1149345
1. Every square kilometer
of the ocean is affected by some anthropogenic driver of ecological change
2. Over 41% of the world’s oceans have medium to very high cumulative impacts:
North and Norwegian seas, South and East China seas, Eastern Caribbean, North American eastern seaboard, Mediterranean, Persian Gulf, Bering Sea, and the waters around Sri Lanka.
3. Lowest impact areas
include high-latitude Arctic and Antarctic poles, but this may change due to
future polar ice loss
4. Ecosystems with highest
impacts include hard and soft continental shelves and rocky reefs, andcoral reefs.
5. Habitat destruction and
alteration; e.g., coastal engineering; tourist development; salt marshes, mangroves, seagrass beds, coral
reefs
6. Input and transfer of
waterborne pathogens (runoff, aquaculture)
7. Air pollution
a. Toxic chemicals; e.g., POP’s over the Arctic zone by airborne volatilization;
b. Mercury
Source: Lavoie, R.A., Bouffard, A., Maranger, R.,
Amyot, M., 2018. Mercury transport and human exposure from global marine
fisheries. Sci. Rep. 8, 6705.
Significance: Human activities have increased the global circulation of mercury,a potent neurotoxin. Mercury can be converted into methylmercury, which biomagnifies along aquatic food chains and leads to high exposure in fish-eating populations.
Trends: Mercury export from the ocean increased over time as a function of fishing pressure, especially on upper-trophic-level organisms. In 2014, over 13 metric tonnes of mercury were exported from the ocean. Asian countries were important contributors of mercury export in the last decades and the western Pacific Ocean was identified as the main source.
Estimates of per capita mercury exposure through fish
consumption showed that populations in 38% of the 175 countries assessed,
mainly insular and developing nations, were exposed to doses of methylmercury
above governmental thresholds.
Given the high mercury intake through seafood consumption observed
in several understudied yet vulnerable coastal communities, we recommend a
comprehensive assessment of the health exposure risk of those populations.
Temporal trends (1950‒2014) of marine fisheries catches (dashed lines) and mercury exported (full lines). (a) Entire ocean (blue) and coastal (red) and high seas (orange) withbreakpoint (circle) ± standard error (horizontal line). (b) Entire ocean (blue) and trophic levels (TL) rounded to the nearest integer: 4 (red), 3 (orange), and 2 (green).
Nutrients (N,P): Eutrophication, Dead Zones
Plastics (shipping, fishing, land-based sources)
Microplastics (nanoparticles; food chain)
Macroplastics (ingestion, entanglement, habitat loss (shorelines))
Ocean plastic
can persist in sea surface waters, eventually accumulating in remote areas of
the world’s oceans.
Our model,
calibrated with data from multi-vessel and aircraft surveys, predicted at least
79 (45–129) thousand tonnes of ocean plastic are floating inside an area of 1.6
million km2; a figure four to sixteen times higher than previously
reported.
Over
three-quarters of the GPGP mass was carried by debris larger than 5 cm and at
least 46% was comprised of fishing nets. Microplastics accounted for 8% of the
total mass but 94% of the estimated 1.8 (1.1–3.6) trillion pieces floating in
the area.
Plastic
collected during our study has specific characteristics such as small
surface-to-volume ratio, indicating that only certain types of debris have the
capacity to persist and accumulate at the surface of the GPGP.
Finally, our results suggest that ocean plastic pollution within the GPGP is increasing exponentially and at a faster rate than the surrounding waters.
Decadal evolution of microplastic concentration in the GPGP. Mean (circles) and standard error (whiskers) of microplastic mass concentrations measured by surface net tows conducted in different decades, within (light blue) and around (dark grey) the GPGP. Dashed lines are exponential fits to the averages expressed in g km−2: f(x) = exp(a*x) + b, with x expressed in number of years after 1900, a = 0.06121, b = 151.3, R2 = 0.92 for within GPGP and a = 0.04903, b = −7.138, R2 = 0.78 for around the GPGP.
On a global scale, between 1984 and 2015, the loss of permanent land in coastal areas amounts to almost 28,000 km2, roughly equivalent to the surface area of Haiti (Fig. a). This is almost twice as large as the surface of gained land (about 14,000 km2) over the same period. On the other hand, the overall surface of gained active zone (about 25,000 km2) is more than two times larger than the surface of lost active zone (about 11,500 km2). Overall, the gain of active zone roughly balances the loss of land, and the gain of land balances the loss of active zone. This translates into a net loss of approximately 14,000 km2 of surface for human settlements and terrestrial ecosystems (Fig. b).
Source: Mentaschi, et al., Global long-term observations of coastal erosion and accretion, Scientific Reports volume 8, Article number: 12876 (2018) On a global scale, between 1984 and 2015, the loss of permanent land in coastal areas amounts to almost 28,000 km2, roughly equivalent to the surface area of Haiti (Fig. a). This is almost twice as large as the surface of gained land (about 14,000 km2) over the same period. On the other hand, the overall surface of gained active zone (about 25,000 km2) is more than two times larger than the surface of lost active zone (about 11,500 km2). Overall, the gain of active zone roughly balances the loss of land, and the gain of land balances the loss of active zone. This translates into a net loss of approximately 14,000 km2 of surface for human settlements and terrestrial ecosystems (Fig. b). Size distribution of cross-shore transition length above 50 m, for erosion and accretion of land (a) and active zone (b). Lost (c) and gained (d) land around the world; lost (f) and gained (g) active zone; balance gained – lost land (e) and active zone (h). Maps show the length of cross-shore erosion and accretion aggregated on coastal segments of 100 km. In all the maps the 4 spots with the highest local transition along a 250 m transect are indicated.
Drivers of shoreline change around the world
List of local cases of erosion/accretion discussed in Mentaschi, et al https://www.nature.com/articles/s41598-018-30904-w The legend provides for each spot a brief summary of the drivers of shoreline change
Land Loss in Coastal Areas: Shoreline modification “masks” true rates of shoreline change along the Atlantic Seaboard
Source: Armstrong, S. B., & Lazarus, E. D.( 2019). Masked shoreline erosion at
large spatial scales as a collective effect of beach nourishment. Earth’s Future, 7, 74– 84. https://doi.org/10.1029/2018EF001070
(R)ecent rates of shoreline change along the U.S. Atlantic Coast are, on average, less erosional than historical rates. This shift has occurred despite evidence of intensified environmental forcing, including acceleration in rates of relative sea‐level rise and increased significant wave height in offshore wave climates. We suggest that the use, since the 1960s, of beach nourishment as the predominant form of mitigation against chronic coastal erosion in the United States…could explain the unexpected reversal in shoreline‐change trends.
Using U.S. Geological Survey shoreline records from 1830–2007 spanning more than 2,500 km of the U.S. Atlantic Coast, we calculate a mean rate of shoreline change, prior to 1960, of −55 cm/year (a negative rate denotes erosion). After 1960, the mean rate reverses to approximately +5 cm/year, indicating widespread apparent accretion despite steady (and, in some places, accelerated) sea‐level rise over the same period.
Cumulative sediment input from decades of
beach‐nourishment projects may have sufficiently altered shoreline position to
mask “true” rates of shoreline change. Our
analysis suggests that long‐term rates of shoreline change typically used to
assess coastal hazard may be systematically underestimated. We also suggest
that the overall effect of beach nourishment along of the U.S. Atlantic Coast
is extensive enough to constitute a quantitative signature of coastal
geoengineering and may serve as a bellwether for nourishment‐dominated
shorelines elsewhere in the world.
Declining Oxygen in the World’s Ocean and Coastal Waters
Source for the following material unless otherwise noted: Breitburg, D., Grégoire, M. and Isensee, K. (eds.). Global Ocean Oxygen Network 2018. The ocean is losing its breath: Declining oxygen in the world’s ocean and coastal waters. IOC-UNESCO, IOC Technical Series, No. 137 40pp. The Ocean is Losing its Breath
Significance:
Insufficient oxygen reduces growth, increases disease, alters behaviour and increases mortality of marine animals, including finfish and shellfish. The quality and quantity of habitat for economically and ecologically important species is reduced as oxygen declines.
Finfish and crustacean aquaculture can be particularly susceptible to deoxygenation because animals are constrained in nets or other structures and cannot escape to highly-oxygenated water masses.
Deoxygenation affects marine biogeochemical cycles; phosphorus availability, hydrogen sulphide production and micronutrients are affected.
Deoxygenation may also contribute to climate change through its effects on the nitrogen cycle. When oxygen is insufficient for aerobic respiration, microbes conduct denitrification to obtain energy. This produces N2O – a powerful greenhouse gas – as well as N, which is inert and makes up most of the earth’s atmosphere.
Impacts
of Excess Nutrients (eutrophication) on ocean oxygen
Nutrients
– primarily nitrogen and phosphorus – from human waste, agriculture and
industry, fertilize coastal waters. In a process called eutrophication, these
nutrients stimulate photosynthesis, which increases the growth of algae and
other organisms (See figure below). This results in more organic material
sinking into deep water and to the sediment. Increased respiration by animals
and many microbes eating or decomposing this organic material uses oxygen. The
consequence can be oxygen concentrations that are far lower than those that
would occur without human influence, and in some cases a complete lack of
oxygen in bottom waters. Strong density differences between surface and bottom
waters (referred to as ‘stratification’), due to temperature and salinity, can
isolate bottom waters from the atmosphere and reduce or prevent re- oxygenation
through ventilation. Semi-enclosed seas (e.g. the Black and Baltic Sea) can be
sensitive to eutrophication and related deoxygenation because of their
characteristic limited water exchange with the open ocean, and low ventilation
rates.
Eutrophication: nutrient flux of nitrogen and phosphorus from human waste, agriculture and industry, fertilize coastal waters
Impacts of excess nutrients (eutrophication) on ocean oxygen. (Figure modified from https://upload.wikimedia.org/ wikipedia/commons/d/dd/Scheme_eutrophication-en.svg)
Deoxygenation Facts
Oxygen Minimum Zones (OMZs)
OMZs areplaces in the world ocean where oxygen saturation in the water column is at its lowest, are shown in blue. Areas with coastal hypoxia are shown in red. Hypoxic conditions are often defined as 2 mg/L O2.
The number of water bodies in which hypoxia associated with eutrophication has been reported has increased exponentially since the 1960s; hundreds of systems worldwide have been reported with oxygen concentrations <2 mg L-1, lasting from hours to years. The increasing severity and prevalence of this problem reflects the invention and increasing use of synthetic fertilizers and the growing human population. Global fertilizer use shown includes data of fertilizers with nitrogen, phosphate and potash.
Distribution of oxygen-depleted ‘dead zones’ in European seas
Oxygen-depleted zones in the Baltic Sea have increased more than 10-fold, from 5 000 to 60 000 km2, since 1900, with most of the increase happening after 1950. The Baltic Sea now has the largest dead zone in the world. Oxygen depletion has also been observed in other European seas in recent decades.
The
Gulf of Mexico dead zone is the world’s
second largest in the world
(The Mississippi River/Gulf of Mexico Watershed Nutrient Task Force, a group working to reduce the Gulf dead zone through nutrient reductions within the Mississippi River watershed, has set a 5-year average measured size target of 1,900 square miles.)
2019 Forecast: Summer Hypoxic Zone Size, Northern Gulf of Mexico
NOAA and the United States Geological
Survey (USGS) released their 2019 forecast for the summer hypoxic zone
size in the Northern Gulf of Mexico on June 10, 2019. Scientists are expecting
the 2019 area of low oxygen, commonly known as the ‘Dead Zone,’ to be
approximately 7,829 square miles, or about the size of Massachusetts. This
prediction is large primarily because of high spring rainfall and river
discharge into Gulf.
Overall, the fixation of nitrogen through Haber–Bosch (120 Tg N yr−1) in 2010 was double the natural terrestrial sources of Nr (63 Tg N yr−1).
The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1natural) is so large it has doubled the global cycling of nitrogen over the last century.
The overall magnitude of anthropogenic relative to natural sources of fixed nitrogen (210 Tg N yr−1 anthropogenic and 203 Tg N yr−1 natural) is so large it has doubled the global cycling of nitrogen over the last century.
Source: Fowler, et al., The global nitrogen cycle in the twenty-first century, Philos Trans R Soc Lond B Biol Sci. 2013 Jul 5; 368(1621): 20130164.
Significance
The supply of Nr–reactive nitrogen (NH3, NH4, NO, NO2, HNO3, N20, HONO, PAN and other organic N compounds) is essential for all life forms, and increases in nitrogen supply have been exploited in agriculture to increase the yield of crops and provide food for the growing global human population. It has been estimated that almost half of the human population at the beginning of the twenty-first century depends on fertilizer N for their food. (Source: Fowler, et al.)
As nitrogen is a major nutrient, changes in its supply influence the productivity of ecosystems and change the competition between species and biological diversity. Nitrogen compounds as precursors of tropospheric ozone and atmospheric particulate material also degrade air quality. Their effects include increases in human mortality, effects on terrestrial ecosystems and contribute to the radiative forcing of global and regional climate. (Source: Lee, et al., see figure below)
Global N budget. Numbers represent global land N storage in TgN or annual N exchange fluxes in TgN yr−1 for contemporary (1991–2005 average) and preindustrial (1831–1860 average in parenthesis) times. See notes for this figure and the table below in: Lee, et al., Prominence of the tropics in the recent rise of global nitrogen pollution. Nature Communications (2019)10:1437 https://doi.org/10.1038/s41467-019-09468-4and Supplementary Table 1 (modified below) and Supplementary Note 1 (https://doi.org/10.1038/s41467- 019-09468-4.)
Current global rate of P fertilizer to croplands* (primary source of P to regional watersheds): 14.2 Tg P/year*
Total P flow through international agricultural trade increased from 0.4Tg to 3.0 Tg between 1961-2011**
The fraction of P taken up by crops that is subsequently exported increased from 9% to 20% between 1961 and 2011**
Global P flows through international trade of agricultural products have become an important feature of the global P cycle, accounting for 20% of the P in global crop production, 17% of the P globally used as mineral fertilizer, and 27% of the P that was traded as mineral fertilizers in 2011.**
Availability drives the
productivity of many aquatic and terrestrial ecosystems worldwide
In agricultural systems,
additional P can be supplied to soils as mineral fertilizer or manure to
support crop growth and sustain high yields
Mineral P fertilizer
production is dependent on the physical and economic availability of mined rock
phosphate resources (non-renewable, diminishing, geopolitically concentrated)
The P cycle has been greatly transformed since the pre-Industrial
era through increased agricultural mineral P fertilizer use
P losses to water bodies
through runoff and erosion from fertilized agricultural soils and from the
inadequate management of animal manure or human excreta has led to aquatic
eutrophication
International trade of
agricultural products (food, feed, fiber and fuel) are a key component of the
global phosphorus cycle; agricultural flows of P are driven by trade of
cereals, soybeans, and feed cakes
28% of global P traded
in human food, 44% in animal feed and 28% in crops for other uses in 2011
The percentage of global population using at least a basic drinking water service rose from 81 to 89% between 2000 and 2015
3 out of 10 (2.1 billion; 29% global population) did not have a safely managed drinking water service in 2015
844 million still lacked even a basic drinking water service
Water-related deaths impact thousands and costs billions
Average annual impact from inadequate drinking water and sanitation services, water-related disasters. Adapted from WWAP (UNESCO World Water Assessment Programme). 2019. The United NationsWorld Water Development Report 2019: Leaving No One Behind. Paris, UNESCO
In 2015, an estimated 2.1 billion people lacked access to safely managed drinking water services and 4.5 billion lacked access to safely managed sanitation services. (WWAP)
Almost half of people drinking water from unprotected sources live in Sub-Saharan Africa, where the burden of collecting water lies mainly on women and girls, many of whom spend more than 30 minutes on each trip to collect water. (WWAP)
Proportion of population using at least basic drinking water services, 2015 Source: WWAP (UNESCO World Water Assessment Programme). 2019. The United NationsWorld Water Development Report 2019: Leaving No One Behind. Paris, UNESCO
Sanitation
Worldwide, only 2.9 billion people (39% of global population) used safely managed sanitation services in 2015. 40% of these people lived in rural areas.
2.1 billion people had access to “basic” sanitation services.
2.3 billion (one out of every three people) lacked even a basic sanitation service—nearly 1 billion people (892 million) still practiced open defecation.
Global and regional sanitation coverage, 2015. Source: The United Nations World Water Development Report 2019: Leaving No One Behind. Paris, UNESCO, 2019.
Total
groundwater volume in the upper 2 km of continental crust is approximately 22.6
million km3 of which 0.1-5.0 million km3 is less than 50
years old1
The
volume of modern groundwater is equivalent to a body of water with a depth of
about 3 meters spread over the continents2
Groundwater
replenished over a human lifetime of 25-100 years is a finite, limited resource
with a spatially heterogeneous distribution dependent on geographic, geologic
and hydrologic conditions3
Accounts for as much as 33%
of total global water withdrawals4
Over 2 billion people rely on groundwater as their primary water
source5
50% or more of the irrigation water used to grow the world’s food is
supplied by groundwater6
Source: 1,2,3–Gleeson, T., Befus, K. M., Jasechko,
S., Luijendijk, E., & Cardenas, M. B. (2015). The
global volume and distribution of modern groundwater. Nature Geoscience, 9(2), 161–167.doi:10.1038/ngeo2590
4,5,6–Famiglietti,
J. S. (2014). The global groundwater crisis. Nature Climate Change, 4(11), 945–948.doi:10.1038/nclimate2425
Groundwater Use by Country, in cubic kilometers per year
Source: Fienen M.N., Arshad M. (2016) The International Scale of the Groundwater Issue. In: Jakeman A.J., Barreteau O., Hunt R.J., Rinaudo JD., Ross A. (eds) Integrated Groundwater Management. Springer, Cham, DOI The International Scale of the Groundwater Issue
37 Largest Aquifer Systems
Source: Map and table): Richey, A. S., B. F. Thomas, M.-H. Lo, J. T. Reager, J. S. Famiglietti, K. Voss, S. Swenson, and M. Rodell (2015), Quantifying renewable groundwater stress with GRACE, Water Resour. Res.,51, 5217–5238, doi:10.1002/2015WR017349
Aquifer Map #
Aquifer Name
1
Nubian
Aquifer System (NAS)
2
Northwestern
Sahara Aquifer System (NWSAS)
3
Murzuk-Djado
Basin
4
Taoudeni-Tanezrouft
Basin
5
Senegalo-Mauritanian
Basin
6
Iullemeden-Irhazer
Aquifer System
7
Lake Chad
Basin
8
Sudd Basin
(Umm Ruwaba Aquifer)
9
Ogaden-Juba
Basin
10
Congo Basin
11
Upper
Kalahari-Cuvelai-Upper Zambezi Basin
12
Lower
Kalahari-Stampriet Basin
13
Karoo Basin
14
Northern
Great Plains Aquifer
15
Cambro-Ordovician
Aquifer System
16
Californian
Central Valley Aquifer System
17
Ogallala Aquifer
(High Plains)
18
Atlantic and
Gulf Coastal Plains Aquifer
19
Amazon Basin
20
Maranhao
Basin
21
Guarani
Aquifer System
22
Arabian
Aquifer System
23
Indus Basin
24
Ganges-Brahmaputra
Basin
25
West Siberian
Basin
26
Tunguss Basin
27
Angara-Lena
Basin
28
Yakut Basin
29
North China
Aquifer System
30
Song-Liao
Basin
31
Tarim Basin
32
Paris Basin
33
Russian
Platform Basins
34
North
Caucasus Basin
35
Pechora Basin
36
Great
Artesian Basin
37
Canning Basin
Global Aquifer Depletion Hotspots in Arid and Semi-arid Zones
Aquifer
Country
Northwest Sahara #2
Algeria, Libya, Tunisia
California Central Valley #16
USA
High Plains (Ogallala) #17
USA
Guarani #21
Argentina, Brazil, Paraguay, Uruguay
Northern Middle East
Iran, Iraq, Syria, Turkey
Arabian #22
Iraq, Jordan,Oman,Qatar,Saudi Arabia, UAE, Yemen
Northwestern India #23
India, Pakistan
North China Plain #29
China
Canning Basin #37
Australia
Adapted from: Famiglietti, J. S. (2014). The global groundwater crisis. Nature Climate Change, 4(11), 945–948.doi:10.1038/nclimate2425
Highlights from Global Aquifer Hotspots: Central Valley, California (#16)
Most productive agricultural area in the United States
40%+ of Central Valley’s water supply comes from gw, primarily to meet agricultural demand
Groundwater use increased from 0.75 to 2.5 km3 per year between 1962-2003
2007-2010 severe drought caused a permanent aquifer system storage loss of ~2%, due to irreversible compaction of the aquifer system
Source: Ojha, et al., Sustained Groundwater Loss in California’s Central Valley Exacerbated by Intense Drought Periods, Water Resources Research, June 2018, 54(5575). Doi: 10.1029/2017WR022250)Most productive agricultural area in the United States
May 7, 2015 – September 10, 2016 Several trouble spots that were identified in 2015 have continued to subside at rates as high as 0.6 meters (2 feet) per year. Significant subsidence was measured in subsidence bowls near the towns of Chowchilla, south of Merced; and Corcoran, north of Bakersfield. These bowls cover hundreds of square kilometers and continued to grow wider and deeper between May 2015 and September 2016. Subsidence also intensified near Tranquility in Fresno County, where the land surface has settled up to 51 centimeters (20 inches) in an area that extends 11 kilometers (7 miles). NASA Earth Observatory map by Joshua Stevens, using modified Copernicus Sentinel SAR data (2016) courtesy of Tom Farr and Cathleen Jones, NASA Jet Propulsion Laboratory. Caption by Alan Buis (Jet Propulsion Laboratory) and Ted Thomas, California Department of Water Resources; edited by Mike Carlowicz.
Declining groundwater storage appears to be part of the Central Valley’s future
Central Valley groundwater storage trends and simulations The GWD Model simulations for both the past and future years. The simulated groundwater storage changes for the years 1980–2014 (Blue line) are compared with observations (red icons). In future years, several precipitation scenarios are examined. Source: Massoud, E., et al., Projecting groundwater storage changes in California’s Central Valley, Scientific Reports 8(1), August 2018. Doi:10.1038/s41598-018-31201-1
One of the largest gw aquifers in the world (8 states; 450,000 km2)
Provides drinking water for 2.3 million people
Extensively used for agricultural production
Storage decline from 1950-2007 accounts for 36% of total gw depletion during 1900-2008
Depletion is highly variable spatially; very high depletion rates in the southern and central HP, large areas of Texas and Kansas. Low/no depletion in the northern HP aquifer (#14)
November 1, 1998-October 331, 2016 The High Plains Aquifer, also known as the Ogallala Aquifer, is under stress. Farmers today have to drill ever deeper wells in order to pump water for irrigation, and one recent study found the aquifer to be under more strain than any other in the United States. About 30 percent of the water once stored beneath Kansas is already gone, and another 40 percent will be gone within 50 years if current trends continue. The map at the left of this page shows irrigation frequency in the basin between 1999 and 2016. Areas watered nearly every year are purple; those watered only rarely are yellow. The extent of the Ogallala Aquifer is shown with gray. The second image highlights the variability in irrigation between center-pivot irrigation fields in an area along the Colorado-Nebraska border. The most widely grown crops in the basin are corn and wheat. NASA Earth Observatory maps by Lauren Dauphin, using data from Deines, Jillian, et al. (2017). Story by Adam Voiland.
1/3 of India’s aquifers are overexploited, semicritical, or critical
70% of India’s agricultural production depends on gw
GW is the primary source (85%) of drinking water for rural areas
GW is typically extracted by tubewells (~15 million)
In Northwestern India (Rajasthan, Punjab, Haryana, including Delhi) gw has been unsustainably depleted between 2000-2008 in an amount equivalent to double the capacity of India’s largest surface-water reservoir (Rodell, et al., 2009)
This region has a population of approximately 114,000,000.
Region supplies nearly half of China’s wheat and one-third of other cereal grains
Population is more than 200,000,000
Rapid groundwater depletion since the 1980’s
Saltwater intrusion into the freshwater aquifer due to groundwater depletion has salinized 44% of the total area between the coastal plain and Laizhou city.
What remains of the large inland lake is a fraction of what it was in the 1950s and 60s. In those years, the government of the former Soviet Union diverted so much water from the Amu Darya and Syr Darya—the regions’ two major rivers—to irrigate farmland, that it pushed the hydrologic system beyond the point of sustainability. During subsequent decades, the fourth largest lake in the world shrank to roughly a tenth of its former size and divided into several smaller bodies of water.
Aswan High Dam, April 12, 2015 NASA Earth Observatory. Astronaut photograph ISS043-E-101953 was acquired on April 12, 2015
EnvironmentalSignificance
Source: Grill, et
al., Mapping the world’s free-flowing rivers, Nature 569(7755):215- 221, doi: 10.1038/s41586-019-1111-9
Destruction/separation of
floodplains from rivers alters ecosystem services such as natural flood
storage, nutrient retention and flood-recession agriculture
Built river infrastructure has
been linked to declines in terrestrial and freshwater species
Sediment capture by dams may
cause alteration of the geomorphic dynamics of rivers and the shrinking of
river deltas worldwide
Inland fisheries provide the
equivalent of all dietary animal protein for 158 million people worldwide
Only 37% of rivers longer than
1,000 kilometers remain free-flowing in their entire length
Only 23% of rivers longer than
1,000 kilometers flow uninterrupted to the ocean
Very long free-flowing rivers are
largely restricted to remote regions of the Arctic and of the Amazon and Congo
basins
In densely populated areas, only
a few very long rivers remain free-flowing, such as the Irawaddy and Saleen
Dams and Reservoirs
the
leading contributors to the loss of river connectivity
There are approximately 2.8
million dams (with reservoir areas >1000 cubic meters) regulating and
creating over 500,000 kilometers of rivers and canals for navigation and
transport and building irrigation and water-diversion schemes
More than 3,700 hydropower dams
(>1MW) are currently planned or under construction worldwide.
2019 Hydropower Status ReportMore than 21.8 Gw of hydroelectric capacity was put into operation in 20182019 Hydropower Status ReportElectricity generation from hydropower projects achieved a record 4,200 terawatt hours (TWh) in 2018, the highest ever contribution from a renewable energy source, as worldwide installed hydropower capacity climbed to 1,292 GW, according to the 2019 Hydropower Status Report China added the most capacity with the installation of 8,540 megawatts, followed by Brazil (3,866 MW), Pakistan (2,487 MW), Turkey (1,085 MW), Angola (668 MW), Tajikistan (605 MW), Ecuador (556 MW), India (535 MW), Norway (419 MW) and Canada (401 MW). Brazil has now overtaken the United States as the second largest producer of hydroelectricity by installed capacity, after 3,055 MW was put into operation last year at the 11,000 MW Belo Monte complex in the country’s northeast.
Small Hydropower Plants (SHP)
Source: Couto, T. B., & Olden, J. D. (2018). Global proliferation of small hydropower plants – science and policy. Frontiers in Ecology and the Environment, 16(2), 91–100.doi:10.1002/fee.1746
Definition: Considerable variability in definition across
countries; refers broadly to facilities that produce less electricity and operate
in smaller rivers as compared to large hydropower plants. Vary greatly in level of flow control,
storage capacity, diversion structures.
70% of countries classify as installations with less than 10 MW capacity
Significance:
There are close to 11 SHPs for every large hydropower plants (LHPs)
= 11% of global hydropower electricity generation
82,891 SHPs are operating or under construction in 150 countries
181,976 new plants may be installed if all potential capacity were
developed
10,569 new projects appear in national plans
China has the world’s largest number of SHPs—47,073; 57% of the
world’s SHPs
Europe has 26,877 SHPs
Future plans for SHPs are concentrated in Asia, the Americas,
Southern and Eastern Europe and East Africa
Environmental Impacts
Similar to LHPs; but SHPs generally occur in
smaller rivers, which is significant given the ecological importance of
headwater streams
Cumulative ecological impacts of SHPs
(multiple installations in the same river basin) appears to be an underappreciated
issue
Freshwater consumption and the global hydrological cycle
“The freshwater cycle is strongly affected by climate change and its boundary is closely linked to the climate boundary, yet human pressure is now the dominant driving force determining the functioning and distribution of global freshwater systems. The consequences of human modification of water bodies include both global-scale river flow changes and shifts in vapour flows arising from land use change. These shifts in the hydrological system can be abrupt and irreversible. Water is becoming increasingly scarce – by 2050 about half a billion people are likely to be subject to water-stress, increasing the pressure to intervene in water systems. A water boundary related to consumptive freshwater use and environmental flow requirements has been proposed to maintain the overall resilience of the Earth system and to avoid the risk of ‘cascading’ local and regional thresholds.” Stockholm Resilience Planetary Boundaries
Status:
Two control variables:
Global–Maximum amount of consumptive blue water use
4000 cubic km/year (4000-6000 km3/yr)
Regional (River Basin)–Blue water withdrawal as % of mean monthly river flow
Source: (Global Hydrological Cycle in the Anthropocene)This commonly reproduced image from the USGS of the averaged depiction of the hydrological cycle does not represent important seasonal and interannual variation in many pools and fluxes. A hydrologic cycle in the Anthropocene should include:
Include anthropogenic influences
Include global teleconnections
Multiple catchments
Endorheic basins
Estimates of green, blue, and grey water use
Estimates of Global Pools and Fluxes of Water
Estimates of pools and fluxes are based on a synthesis of approximately 80 recent and global-scale studies; volumes represent the central point of the most recent or comprehensive individual estimates. Adapted from Abbott, et al., Nature Geoscience 12, 533–540. 2019
Based on the figures in the previous table, human appropriation (~24,000 km3yr-1) redistributes the equivalent of half of global river discharge or double global groundwater recharge
Irrigated agriculture is the largest water consumer, accounting for ~85-90% of water consumption, followed by industrial, and domestic water use
Global water consumption rose 40% between 1980 (~1,200km3) and 2016 (~1,700km3).
Top Six Water Stressed River Basins by Continent 2012-2016 5-year Index
In each continent, the basin is selected as the one having the
largest water stress index among the top 10% basins that have substantial
electricity generation, crops production, human population, livestock and dam
capacity in each continent.
Source: Wu, N., Wang, C., Ausseil, A. G., Alhafedh, Y., Broadhurst, L., Lin, H. J., Axmacher,J., Okubo, S., Turney, C., Onuma, A., Chaturvedi, R. K., Kohli, P., Kumarapuram Apadodharan, S., Abhilash, P. C., Settele, J., Claudet, J., Yumoto, T., Zhang, Y. Chapter 4: Direct and indirect drivers of change in biodiversity and nature’s contributions to people. In IPBES (2018): The IPBES regional assessment report on biodiversity and ecosystem services for Asia and the Paci c. Karki, M., Senaratna Sellamuttu, S., Okayasu, S., Suzuki, W. (eds.). Secretariat of the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services, Bonn, Germany, pp. 265-370.
Over 2 billion people live in countries experiencing high water stress. Recent estimates show that 31 countries experience water stress between 25% (which is defined as the minimum threshold of water stress) and 70%. Another 22 countries are above 70% and are therefore under serious water stress.
It has been estimated that about 4 billion people, representing nearly two-thirds of the world population, experience severe water scarcity during at least one month during the year.
Global overview of countries experiencing different levels of water stress (the ratio of total freshwater withdrawn annually by all major sectors, including environmental water requirements, to the total amount of renewable freshwater resources, expressed as a percentage). Source: WWAP (UNESCO World Water Assessment Programme). 2019. The United NationsWorld Water Development Report 2019: Leaving No One Behind. Paris, UNESCO
Trends in Terrestrial Water Storage (TWS) April 2002-March 2016
Adapted from Rodell, et al. 2018; based on Figure 1 and Table 1 Terrestrial Water Storage = Groundwater + soil moisture + surface waters + snow + ice
