Instant Genius - Drought, with Kevin Hiscock

Episode Date: August 11, 2022

Kevin Hiscock, a professor of environmental sciences at the University of East Anglia, unpacks the problems the UK is facing with drought and how to tackle them. Hosted on Acast. See acast.com/privacy for more information. Learn more about your ad choices. Visit podcastchoices.com/adchoices

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delivering digital precision with analogue warmth. So you can experience exceptional sound at home. Music just as the artist intended. Visit name, Hello and welcome to Instant Genius, a bite-sized matter class in podcast form. I'm Jason Goodyear, commissioning editor at BBC Science Focus magazine. In this episode, I speak to Kevin Hiscock, professor of environmental sciences at the University of East Anglia. He tells me what we should be doing to protect the UK's water resources

from future droughts. There's been lots of reports in the news recently that this is one of the driest years on record for some decades now. And I think, certain parts of the country have gone for around 150 days without seeing any rainfall. So this has led a lot of people to say the UK may be heading for a drought. So people use this term a lot, but is there a strict scientific definition of exactly what we mean by a drought? No, there isn't actually a strict definition. You can think in terms of a meteorological drought, in terms of a deficit of rainfall, like we see in the last few months. agricultural drought, particularly if that dry weather is at the same time as the irrigation season in the summer,

or I also think in terms of hydrological drought, and they're perhaps the worst in respect of maintaining the water supply for both our drinking water, but also to support the environment. But they develop over a longer period than several weeks of no rainfall. but the recent period, we've seen months of lower rainfall than usual. So one dry spring leading into another dry autumn winter makes the problem worse. So next year, we could see more of an issue if we don't actually get some rainfall over the critical winter period, the recharge period, as we think about in hydrology. And also, I think that how severe the drought depends on where you are geographically. So when I think back to 76, the drought then was mainly in the north and the west,

where there's very little in the way of groundwater to support supply or river base flow. So that was particularly severe then. But this year we're seeing dry weather everywhere. So even where we do have groundwater resources in the east and in the south, in the chalk aquifer, even those are stressed. So it depends a bit on the geology, the weather pattern and the longevity of that. dry period, but certainly now we're finding that the drought is developing. Yeah, so you mentioned there groundwater. So I think before we get into the sort of the more sort of nitty-gritty of these

things, so could you give us a brief overview of how water moves through a landscape where it's stored and that sort of thing? Yeah, well, typically river flow, particularly in the east and the south where we do have extensive aquifers, much of that river flow is groundwater, perhaps 75% or more. So the rainfall infiltrates the soil zone and then slowly moves down to the water table. And then gradually that water will move towards the discharge area, which is the river or it could be a wetland, for example. So a surface water dependent system dependent on the groundwater. So much of eastern and southern England is underlain by the chalk. And that chalk is a huge reservoir of water. I mean, one third, of the drinking supply in England will be from the chalk aquifer.

So one of the first steps a water company can do in a period of low rainfall is to switch some of its supply, if it has groundwater, to take more groundwater. It's a very typical response to turn to groundwater in a drought, which in itself, over a long period, can be an impact on the groundwater. But essentially, we've got this large water cycle, rainfall, infiltration, groundwater discharge, into the river and then down to the estuary, back out to sea, to connect up to the water cycle. But groundwater is really important for our river flow and for our public supply in the south of England. So what is the situation with sort of UK water resource management at the moment?

How well or how poorly are they being managed? Well, all water companies do go through a five-year planning cycle, the so-called AMP period, the asset management period cycle. And they should be looking at their longer-term projections for demand. That will take into account population increase as well as climate change factor. So they should be building in what they call headroom into their forecasts. But when you look at the eastern region, there the forecast is an increasing population, an increased drought climate.

And so insufficient water is available in the longer term. So you've got to plan to build storage into the system. So in the Anglian region, for example, presently there's discussion of building one, if not two new surface reservoirs with which to fill the reservoir during the winter when there's an excess of water to have it available in the summer. So we do need to build headroom. and it depends on the nature again of your geography, whether you have groundwater resources that you can use, whether you're entirely dependent on surface reservoirs, like you may be more in the west of the country, in the north of the country. You can also move resources around in a region. That's another way.

So, for example, in the wetter northern part of Britain, you could divert water southwards, which we see presently with a big pipeline being built from Humperside down through. to Essex at this time to try and redistribute the resource. So in the east and the south, with growing population pressure and climate change scenarios, we do need to think about how to build more storage. We also have, I feel, an historical legacy of where we've placed, our sewage treatment works, the larger works typically are at the bottom end of the catchment. And that relates back to the 19th century when rivers were very contaminated with sewage. And the idea of just getting that sewage out to sea as quickly as possible was what was the need at that time.

But of course, that sewage water is highly treated. We can see it as water recycling, if you wish. But we then put it into the estuary and we lose it out to sea. So one thing we could do is move our sewage outfalls further back up the catchments. so is to be able to use that water again. And the public sometimes find that distaste or the idea of having water that's been recycled through the human gut. But it's not unusual between Oxford and Teddington on the Thames.

That water is reused seven times. So essentially it's abstracted, recycled through the sewage works and back into the river. So it's not a new concept. But historically, a lot of our sewage works are at the bottom end of catchments. And so we lose that recycled water going out to sea. So we could reposition those outforce. And that has happened in one of two cases, but it could be part of a strategy to build a bit more resilience

into the water supply system. But yes, water companies are required to make these plans, and these plans are then looked at by OffWAT, the government regulator, and then off-watt determine whether or not the plans are affordable for the public in respect of how big our water bills would need to be to increase that resilience through building infrastructure. So there's a need to control the price of water that we, the price that we pay for water. So the water companies make a bid to OffWAT to build

a system, to build in that resilience, but whether it's affordable is determined by off-WAT, then determine how much our water bills can go up. So like people often talk, in situations like this about hose pipe bands and people get annoyed that their lawns are going brown or they can't water their roses. But there are more significant impacts than this, aren't they? Like specifically on agriculture. Yes, agriculture and the environment. I mean, yes, reduced food yield. So that's not good, obviously. We're seeing now, aren't we, crops that are just dying in the fields. Peas, for example, I've noticed. Some farmers are still continuing to irrigate, so they are able to do that presently, so that helps protect the potato

crop. The Environment Agency do have the power to stop farmers from irrigating, so-called Section 57 of the Water Act. That is when the farmers particularly get upset when they spend a lot of money on irrigation equipment and then being told to not use that equipment. But this summer period, farmers have been able to continue irrigating. We're towards the end of the season now, so that's been quite good. But when I think back to the drought of 89 through to 92 in the Anglian region, then there was a ban on irrigation, and the farmers were very unhappy with that.

And so you get this classic conflict of interest between the need to protect the water for public supply, and the need for water for irrigation, and also you have to leave some water in the catchment within the water balance to maintain the river flow and so protect the environment. But even that can be mined into, if I can use the word mining of a water resource.

So under drought orders in worse situations, which we've seen in the past, water companies can take more water from a river or from an aquifer, more than they're entitled to do under their license. And the government would have to decide upon those drought permits. because by taking more water from the ground or the river, you're ultimately going to damage the aquatic environment.

But that drought order step, we haven't got to yet in this current drought. We've got as far as bands on host pipes and sprinkler, so-called temporary use bands, but we're a couple of steps away yet from drought orders, which we have seen in the past. So in some ways, to get things into perspective, this drought is developing, but hasn't got to a point yet where it could be,

even worse. This is why at the beginning I was saying a dry winter following this period would be a much more serious situation for next year. But at present, certainly wildlife is suffering, the low flow in the rivers. It doesn't look very good. It's warmer temperatures, reduce the oxygen content, so that stress for fish. There are fewer, deeper pools of cooler water for the fish-defined refuge. We also see a dilution of chemicals in the river. So you'll seeing a lot more on the way of algal growth on the surface of the river. So this is just another problem, which is, of course, diffuse runoff of aquacultural contaminants like fertilizers, sewage inputs, all those nutrients that cause algal growth, which with warmer temperature

also grow more quickly. So we're seeing stress indirectly through warmer temperature, lower flows, and these pollution sources creating the algal eutrophication situation, which also reduces the oxygen content. So it's not a good picture out there at the moment because of the lack of rainfall affecting the water in the river. But in terms of the water balance, the hydrology, then the situation is not so bad yet. must to require drought permits or drought orders. A drought permit is where you can take more water from a river than you're allowed to do under your licence. So we mentioned earlier this impossible sort of infrastructure-based solutions

such as these pipelines running up and down the country and placing the sewage works in a position where we can recycle the water. What about other sort of land management solutions like planting woodlands? Could that help? I think that's a good point. Yes, planting woodland, introducing beavers into the landscape. They're very effective water engineers. Also ways of cultivating the ground to create a more textured soil so that infiltration occurs more easily.

So you find that with approaches like regenerative farming or, let's say, minimum tillage approaches to avoid plowing of the soil, which upsets the soil structure. If we can help build the soil structure, increase the organic content in that soil, it becomes more fibrous, and is able to, like a sponge, withhold the water and also allow infiltration to occur. And conversely, to avoid flood runoff suddenly in a storm.

And so you lose that water rapidly into the river system, and in fact it would be beneficial to allow that infiltration to occur to the water, table and so maintain that large groundwater store that is so important for supporting the river environment. So yeah, we can change or increase those sorts of approaches to cultivation, to enhance infiltration. Building, well, yeah, building or planting woodland certainly does help slow down the flow and therefore you don't lose the runoff quite so quickly into the river channels. So that again, like a big sponge in the riparian zone. So anything that slows the flow

like that and allows infiltration more chance to occur is beneficial. Of course, when I think that through, that's a good thing to do because it avoids rapid runoff and loss out to sea quickly. But if we have no rainfall, there be no infiltration. But where we do have some rainfall, we can maximize the infiltration. That's all all to the good. And then I also think that we can extend those ideas into the built environment. So when you think about the amount of concrete and tarmac in urban areas and how quickly, say, a summer storm, you see flooding in the urban area in a heavy thunderstorm in the summer and then it all runs away quickly into the drainage system and again into the river and lost out to sea. If we can increase the range of green space

in the city area, so what we call sustainable urban drainage systems or suds, so suds are things like ponds or wetlands within a new housing development. There might be a pond in the centre of the development where the drainage from the roofing and the driveways goes into and then can seep again into the water table. So greening up our urban space, thinking in terms of these sustainable drainage systems, another good way of holding that water in the catchment. I think the Chinese have a term for this. I think they call this approach sponge cities.

So if we can have more sponge cities, I think that would be all to the good. So we need to be able to influence our construction industry to think about building those drainage systems into new buildings, and indeed in new buildings, installing more water-efficient appliances. And so increasing,

water efficiency in our own homes, which is the other big area that we should perhaps discuss our behaviour towards our water usage. I mean, there are differences when you look globally, the US, for example, per person per day, is on the order of 600, well, perhaps 500 to 600 litres per person per day. It's quite high use, if not profligate use of water. In the UK, it's about 140 litres per person per day. But we're not the best in Europe. In Germany, they achieve 120 meters per person per day. So our behaviour is a little different to the German population. They are more efficient and they use their water perhaps a bit more wisely, maybe. We have a bit of a disconnect always in this country, in the UK. If you ask someone on the street,

where does your water come from? They don't think about the river or the groundwater. They will say it comes at the tap, which just shows there's an expected service that they pay for and require. But, of course, that water has to come from somewhere. So if we can improve understanding of where that water comes from, and in a drought, of course, people do wake up to the fact that a water shortage is beginning to affect our supply. But normally, people don't give that quite so much thought, and therefore they don't tend to change their behavior as much.

So I think water metering can be a way of assisting that education of people as to how they use their water. I mean, in some regions, there is high water metering, but in some regions less so. So continuing work to install water meters may help to change our behavior a little. Yeah, that was, that's very similar to something that I was going to ask. Is there any sort of, so we mentioned the big infrastructure things, the pipelines, the forests, the wetland management and that sort of thing. But is there any advice that you could give to our readers and listeners and how they can help the situation?

Yeah, I think we all help. So, yes, at this time, not using a hose pipe or a spring class, terribly inconvenient. I know for those keen gardeners, like myself, for example, having to walk around the garden, endless watering cans. So, yes, we can reduce our use in that way. Putting on the dishwasher or the washing machine when it's full, and reduce our use of those appliances. Well, when we have water, of course,

it's great to be able to capture that water to harvest it in a water butt, say, so you can use that water butt for watering the garden during a dry spell, although my three water butts are all now empty because of this long dry spells. But in an ordinary year, a water butt can help reduce your use of tap water to water the garden. So rainwater harvesting, I mean, others go as far as saying you could try and siphon off the bath water and use that for grey water in the garden. But you could say perhaps take a shower and not have a bath in the first place. So taking showers, using the washing machine less, harvesting the water where you can. These are all steps that we can take.

But ultimately, in the longer term, then buying those water efficient appliances, I mean, I'm amazed to see that we never have. have a label on, say, a wash machine telling us how water efficient it is. There's an energy efficiency label. I know the government, under its plans, want to see more widespread adoption of using water efficiency labels, if not mandatory labeling of equipment. And also leakage on our own properties. If your water meter continues to turn, then there's an issue with some form of leakage on your side of the water network. And that's another area. We often criticize water companies not doing enough to stem water leakage, but often it can be a problem on the customer side. And water companies should do more to encourage homeowners to look at

that problem. So leakage is a difficult thing to overnight cure. I know there's pressure now and people link that to the performance of water companies, they do have plans. Honestly, if you try and dig up all the water pipes in one go, you're going to disrupt a lot of people in terms of digging up all the roads. So it's an ongoing process of trying to reduce leakage. But yeah, leakage is another area that we can work at, clearly, to reduce loss of that water at raw supply,

which will, I think, become less in-supply. in terms of climate change scenarios, we think ahead into the future, periods like this will become more frequent. This is the best that we can see from the climate modelling scenarios, even though there's uncertainty around predicting, particularly summer rainfall totals. It's difficult to make those predictions.

And then if you try and use those predictions to then drive a hydrological model, those models themselves have uncertainty. So you see this cascade of uncertainty through the climate modelling into the hydrological modelling. But our best estimates, these scenarios that are for the future climate, do suggest in the south and east of England, increasing summer drought frequency and more intense drought and indeed over wider areas. But that's not for the whole of the UK.

As you go towards the northern part of the UK, the scenario there, is for normal or wetter conditions, so not quite the severity that we might expect in terms of droughts in the future. And the other characteristic that I always notice in terms of climate scenarios from a hydrological perspective is that all-important winter rainfall when we need the recharge to occur to top up our aquifers that support our rivers, which we then take water from for our supply. that all-important winter recharge will occur on fewer days. So the winters will become wetter, but the rainfall will be on fewer days. So we'll see an increased flood risk, but also that short period, that runoff, it occurs as a flood. We've got to capture that to store that, to then also get through the following, what will be a longer, drier summer period.

So the intensity will change. The number of rain days will change as well. So the southern areas will get dry and the northern areas will get a little wetter. That's the general pattern. So it's like increasing the gradient between dry and wet from south to north. So that winter storage is all important

if we're going to get through those longer summers in the future. So what do you think the picture's going to be then for the coming years? Are you optimistic that we'll be able to deal with this if we act properly? Well, we're back to those forecasts for the future. The water companies undertake, they typically look out 25 years into the future, beyond which it becomes even less certain as to what the scenario will be. So, yes, we are planning for drier summer periods and increased population,

well, particularly in the east of the country, there's a growing population there. And we're not going to get through that unless we do have this increased storage. So we turn into that idea of building infrastructure to store water and reservoirs. That's very contentious, of course, because that reservoir is a large area, and it means there will be displacement of some activities due to the drowning out of that land. But when we've talked about new reservoirs for as long as I've been a hydrologist, decades in other words, plans for a reservoir in South Oxfordshire, a plan for a reservoir out in the Fens in East Anglia. They've been talked about for a number of years, but they may well have to become a reality

if we're going to be able to cope with future for summer periods, given the need to store water. Another thing that we can do is actually directly recharge aquifers. So in some parts of the world, the idea of recharging the ground. with water, so-called managed aquifer recharge, is quite a common technology. We don't do that much in this country. There's a small-scale pilot presently near Felixstowe in the sands and the gravels there, in the crag aquifer. The idea there is to store water in the ground, which of course has less of a visual impact by storing the water in the ground, and then pumping it out in the summer for irrigation purposes. That part of East Anglia is well known for its sandy soils,

very good for growing asparagus. So we can develop managed aquifer recharge. The biggest example we have in this country presently is the North London scheme. So there's an artificial recharge scheme in North London in the River Lee Valley. So in the wintertime, Thames water can pump treated tap water, which is in excess at that time. from the mains into the ground, into the chalk boreholes. And the water fills up the chalk and the overlying sands. And then in the summer, during a drought, they can then pump those boreholes and tap into that store

that they have built up during the winter. They last used that scheme back in the mid-1990s, whether they will need to use that soon, I don't know for sure, but they certainly have the ability to store water underground. what we would call managed aquifer recharge and then recover that during the dry period. So that's attractive because it has less of a surface impact compared with a surface reservoir.

It's quite common around the world, but not so common here, partly because of our geology once again. In many parts of the world, the aquifers are gravel, sand, silts, but here we typically have sandstones and limestones, which are not so easy to develop. They're hard rocks,

and they're very thick, so not quite so straightforward. Yeah, so that's covered all the questions that I had then, unless there's anything important that you think we've missed, that you'd like to add. No, I think we've covered a great deal there, actually. So, yeah, thank you for the opportunity to tell you all about what is not necessarily a straightforward situation when there's a drought. Yes, there's a drought, but will it be a hydrological drought,

which will then really affect our water supply? the reason you're seeing host pipe bands in the south of England is because on the south coast, the chalk water level is very low at the moment. So clearly there's an issue there and they depend on that chalk a lot, so they've got to conserve that storage. So yeah, we'll see how it develops in the next few months. But I'm just hoping that as in 2012, the drought will come to a sudden end and we'll get copious rainfall. As happened in 1976, come the autumn, it just didn't stop raining.

and then the whole problem went away. But it's not going away now. With climate change, we can expect the situation more in the future, so we have to build that resilience. Thank you for listening to this episode of Instant Genius. That was Professor Kevin Hiscock. The current issue of BBC Science Focus magazine is out now. Pick up a copy in stores or visit ScienceFocus.com.

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