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> The hydrological model, published in the journal Nature, shows that in nearly 20% of regions that pump groundwater, rivers are already flowing too low to main
by EndXA 7y ago
> The hydrological model, published in the journal Nature, shows that in nearly 20% of regions that pump groundwater, rivers are already flowing too low to maintain healthy aquatic ecosystems.
This refers to this study: https://www.nature.com/articles/s41586-019-1594-4 https://www.nature.com/articles/s41586-019-1594-4
Abstract:
> Groundwater is the world’s largest freshwater resource and is critically important for irrigation, and hence for global food security1,2,3. Already, unsustainable groundwater pumping exceeds recharge from precipitation and rivers4, leading to substantial drops in the levels of groundwater and losses of groundwater from its storage, especially in intensively irrigated regions5,6,7. 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.
- donkeyd 7y agoI'm not sure if it's reasonable, but I'm starting to think that the amount of people that are currently inhabiting earth is just not sustainable. We are inhabiting many places that high risk for the people living there (fault lines, hurricane paths), we're exhausting resources and causing plants and animals to go extinct. And, according to this article, we're also exhausting groundwater reserves. Meanwhile, projections show that probably another couple billion people will be added in the next three decades. There's strong resistance against any proposals to cut back emissions, especially if it means giving up some of the luxury we're used to (flights, meat, cars, large houses, etcetera). I might have a bleak perspective of the current state of affairs, but I'm really not seeing any feasible short term solutions, that can actually get people on board. Naming possible solutions is easy, but getting everyone to agree seems downright impossible for the foreseeable future. And I fear that we won't change a thing before it's too late.
- dmitriid 7y agoI think he number is sustainable. However, we are overproducing, and we are ineffective in distributing food and goods. And most of that ineffectiveness comes down to politics.
- snarf21 7y agoI agree. I don't think the earth can support more than about 4B or so people. Our aquifers are drying up and they can take centuries to refill. Or they compress and will never fill again (but maybe new ones will instead). We have no real chance of changing human behavior so it seems like we just need less humans. I'm not suggesting laws but you can remove tax breaks for kids after the second. Have all you want, you just don't get the breaks. I think the earth is about to strike back and show us who is boss. Clean water, food monoculture, and antibiotics overuse are going to come home to roost and we'll quickly learn what a sustainable population is.
- dredmorbius 7y agoThe long-term historical trend was far closer to 50-100m. There are very few historical large wild mammal populations remotely close to this. And historical, because we've reduced wild terrestrial vertebrate biomass by about 90% over the past 100-1000 years. There are about a half-million wild zebra, and maybe 12 million white-tail deer. The largest seal populations are estimated at about 8 million -- roughly the number of people in New York City. We're probably outnumbered by brown rates, roughly 11 billion. Even of domesticated cattle and pigs, totals are on the order of about a billion. The passenger pidgeon, two centuries ago, numbered 3-5 billion individuals. Today there are none. For most large terrestrial mammals, populations are in the 5,000 - 50,000 range. That's the population of a small to mid-sized town. For an entire species. Update: an Imgur photo gallery consisting of images with as many pixels per image as there are individuals in the population: https://imgur.com/gallery/9v4HV2p https://imgur.com/gallery/9v4HV2p
- wbl 7y agoDesalination is used extensively by Israel.