Stor­ing water to cope with droughts

Farm­ers in Swe­den, France and Ger­many are striv­ing to retain water when there is plen­ty avail­able so they can use it dur­ing dry sum­mer months. Water is stored in ponds, marsh­es, or in the ground. The Fur­row reports.

Sum­mer 2018: In Swe­den, tem­per­a­ture records were being rewrit­ten almost dai­ly. Some areas went for three weeks with­out rain, a first in this north­ern cli­mate. Nick­las Görans­son, farm­ing 300ha of pota­toes, onions, car­rots and grain, saw his yields fall by 25% dur­ing the sea­son as his piv­ot irri­ga­tion did not allow him to coun­ter­bal­ance the effects of heat, due to a lack of water. “We couldn’t irri­gate the small grain,” he recalls a year lat­er.

His pota­toes yield­ed only 30-40t/ha, 10t less than expect­ed, and his onions 40t/ha instead of 50t. Bar­ley yields fell by 25%. Still, he did bet­ter than many of his col­leagues – accord­ing to the Lant­män­nen coop­er­a­tive, the aver­age Swedish grain yield fell by 45% in 2018.

Warm­ing

Through­out Europe, droughts are putting more and more farm­ers under pres­sure. In a sce­nario of high car­bon emis­sions, heat waves like those of the last two years, or even more intense, will be repeat­ed every two years in the next 30 years, accord­ing to the Euro­pean Envi­ron­ment Agency. This would increase irri­ga­tion needs by 25% by 2100. In the south­ern part of the con­ti­nent, non-irri­gat­ed field crops could expe­ri­ence yield drops of up to 50%.

A wor­ry­ing sit­u­a­tion. How­ev­er, aver­age annu­al water resources remain sta­ble in most coun­tries, and have even increased in some (info­graph­ics p12). Pre­serv­ing water when it is avail­able in order to use it lat­er is there­fore a com­mon-sense approach. Reten­tion basins, hill­side reser­voirs, and agro­nom­ic solu­tions exist, and more and more pro­duc­ers are con­sid­er­ing them.

Swe­den: invest­ment in the future

In ear­ly 2018 Mr Görans­son start­ed con­struc­tion of his water reten­tion sys­tem, which was com­plet­ed a year lat­er. It con­sists of a 30,000m3 drainage-fed basin cou­pled with a wet­land, and is con­nect­ed to the near­by Hel­geån Riv­er. The drained water flows into the basin and when it reach­es sat­u­ra­tion a pipe redi­rects excess water to the marsh, where it is stored. Con­verse­ly, if there is not enough rain to fill the pond and marsh­land, water from the Hel­geån Riv­er can be used.

The marsh­land brings bio­di­ver­si­ty.

Nick­las Görans­son

“It’s an invest­ment in the future,” says the pro­duc­er. Two thirds of his irri­gat­ed areas are still sup­plied by a self-drilled well, but the neigh­bour­ing town of Kris­tianstad is plan­ning to use ground­wa­ter as well. Mr Görans­son there­fore expects quo­tas to be set on how much ground water can be tak­en out. “Before the reten­tion sys­tem was built, I was much more vul­ner­a­ble to future reg­u­la­tions and restric­tions.”

He under­lines the sus­tain­abil­i­ty of his approach: “It would not be sus­tain­able in the long term to use only pure drink­ing water to irri­gate our crops. I am not allowed to use more water than my farm pro­duces. But the marsh­land brings bio­di­ver­si­ty.” The 2.5ha of wet­land was eli­gi­ble for aid mon­ey cov­er­ing 90% of the estab­lish­ment costs, name­ly SEK2.5m (£209,000).

France: a basin for veg­etable grow­ing

Fur­ther south, France has not been spared from the chang­ing cli­mate. In 2019 alone, the FNSEA (Nation­al Fed­er­a­tion of Farm­ers’ Unions) esti­mat­ed eco­nom­ic loss­es due to the drought to be €80m (£72.5m). In Print­zheim, Alsace, Antho­ny Car­bi­ener can tes­ti­fy to this. The young farmer and his par­ents work 91ha, main­ly grow­ing veg­etable crops (squash, pump­kin, cab­bage, cour­gettes, aspara­gus, Chi­nese cab­bage, and let­tuce). Del­i­cate pro­duce in the con­text of cli­mate change.

“The farm began mar­ket gar­den­ing in 2000,” reports Mr Car­bi­ener. “We nev­er need­ed to irri­gate until 2003. Now we’ve run out of water.” The first drought expe­ri­ence was in 2014. “And from 2017 onwards, we have been hit hard.” Plants are not only impact­ed by the water deficit but also by the heat, which is unavoid­able. “Bloom­ing crops are the ones that suf­fer the most. Dur­ing the last heat wave, they start­ed to wilt as ear­ly as 10am.” In the green­house where the fam­i­ly grows toma­toes, pep­pers and aubergines for direct sale, the tem­per­a­ture rose to 70°C.

The vol­ume of rain shifts through­out the year.

Antho­ny Car­bi­ener

In 2018, the fam­i­ly decid­ed to build a reten­tion basin to make up for the lack of water – hav­ing just lost 70% of their veg­etable har­vest. “The prob­lem is that Print­zheim doesn’t lie over any ground­wa­ter,” explains Mr Car­bi­ener. “We tried to drill a well, but we’d have to go down to 600m to get the 70m3 per hour we’re look­ing for.” Instead, the farm invest­ed €55,000 (£50,000) in a 60 x 60m basin, five metres deep, with slopes of 35°. That’s a 12,500m3 reser­voir, mak­ing it the largest arti­fi­cial basin in the region. It will fill up direct­ly thanks to the abun­dant win­ter rains, and through the drainage water from the sur­round­ing 150ha.

Effi­cient irri­ga­tion

A few years ago, Antho­ny Carbiener’s par­ents start­ed grow­ing veg­eta­bles so he could work on the fam­i­ly farm. Now, water stor­age has become nec­es­sary to sus­tain this pro­duc­tion.

“The vol­ume of rain shifts through­out the year,” observes the veg­etable grow­er. In the mid­dle of the cab­bage har­vest, intense rain­fall com­pli­cat­ed field work. And it’s get­ting hard­er and hard­er to get onto the fields in the spring. “At the begin­ning of April, we had a long warm peri­od, fol­lowed by a peri­od of heavy rain at the begin­ning of May. And then, from 15 May: No more rain until Sep­tem­ber,” says Mr Car­bi­ener. “This has been the recur­ring pat­tern for sev­er­al sea­sons now.”

The basin allows him to irri­gate between sev­en and 15ha, depend­ing on the year. This is not a guar­an­tee against drought but does pro­vide more room for manoeu­vre. “The vol­ume of water would allow more land to be irri­gat­ed, but the next plots are 4km away. It would be too expen­sive to pump water all that dis­tance. Then we have to opti­mise our crop rota­tion.”

Pre­serv­ing water in the ground is anoth­er pos­si­bil­i­ty. “We start­ed mulching the cour­gettes for weed con­trol, and we saw a reten­tion ben­e­fit.” Mr Car­bi­ener now sys­tem­at­i­cal­ly uses a 1.5m nylon sheet on both sides of the row along with drip irri­ga­tion. “If cour­gettes do not have a reg­u­lar grow­ing cycle, the fruit will be deformed and impos­si­ble to sell at the main buy­ing cen­tres.” The mea­sures put in place have enabled him to halve the vol­ume of irri­ga­tion water required.

For sev­er­al years the farm has also been work­ing to improve its soil organ­ic mat­ter. “In mar­ket gar­den­ing, we spread com­post at a rate of 60m3/ha every year.” After har­vest, nitro­gen fix­ing crops are sown. “Times are chang­ing rapid­ly, and not every­body will be able to cope with it, but we’re already see­ing the ben­e­fits,” says Mr Car­bi­ener.

Ger­many: nat­ur­al water reserves

Wind­break hedges pro­tect against ero­sion on Peter Kaim’s land.

At the begin­ning of Decem­ber, not far from Berlin, the east wind freezes you right down to your bones. It’s hard to believe that Peter Kaim, who runs a mixed crop/livestock oper­a­tion in Nauen with 1,000ha and 170 dairy cat­tle, had to cope with a heat wave last sum­mer. And yet it was his region, Bran­den­burg, that suf­fered the most from the heat wave in  Ger­many. It rained more than in 2018, but not enough to make up the deficit. “We real­ly have had two bad years behind us,” he says. In April 2018, spring “nev­er came”.

“We went straight from win­ter to sum­mer. Then there was almost no rain all sum­mer,” says Mr Kaim. On the non-irri­gat­ed land with sandy loam and silty-sandy soils, yields were heav­i­ly affect­ed: -30% in bar­ley, -50% in corn, -70% in Eng­lish rye­grass. Only a few plots on a for­mer peat bog drained in the 18th cen­tu­ry, where the ground­wa­ter lev­el is high­er, did bet­ter. “The cli­mate has been chang­ing for 25 years,” says the farmer. “I can’t change any­thing about that. On the oth­er hand, I can change the way I think and work.”

Since 2007, Mr Kaim has been grad­u­al­ly mov­ing towards min­i­mum tillage, with the aim of sav­ing water, lim­it­ing ero­sion and increas­ing humus lev­els. In the begin­ning it was not the weath­er that moti­vat­ed him to change his sys­tem but the fall in rye prices. The goal was to reduce his work­load. “After the first seed­ing with­out till­ing, I could see that the crop was grow­ing well.” Mr Kaim quick­ly recog­nised the ben­e­fits of this tech­nique for soil health and its water cycle.

Strip-till and inter­im crops

He reserves sev­er­al plots for tri­als. Mr Kaim has observed the effect of the delay between tillage and sow­ing on yield (-20% in rape­seed for a 10-day dif­fer­ence). Where he does cul­ti­vate he sows the crop right after the cul­ti­va­tor has passed over, in order to leave the soil open for the short­est time­frame pos­si­ble to avoid water loss. Last sum­mer, he even worked overnight to lim­it evap­o­ra­tion.

For the past three years, he also used strip-till as an alter­na­tive to direct seed­ing. The dis­tur­bance to the soil is min­i­mal: The machine only opens it pre­cise­ly where the row of seeds is sown and adds slur­ry if nec­es­sary. The plant ben­e­fits from the localised organ­ic fer­tilis­er and the pre­served humid­i­ty, as the soil remains most­ly cov­ered.

Soil isn’t meant to be bare. It should stay cov­ered to stop it dry­ing out.

Peter Kaim

In addi­tion he has adapt­ed rota­tions to sim­pli­fy cultivation tech­niques. Mr Kaim usu­al­ly fol­lows rape­seed with no-till rye, corn, win­ter bar­ley and, final­ly, wheat. But this is just one pos­si­bil­i­ty among many. “Rota­tion is the system’s cor­ner­stone. With more crops, it’s eas­i­er to jug­gle.” Rape­seed is only grown every five years.

In each case, he weighs up the pros and cons of direct seed­ing and – based on the spe­cif­ic con­di­tions of each plot – decides whether to incor­po­rate the residues. Many farm­ers still leave their fields uncov­ered dur­ing the win­ter months to take advan­tage of freeze-thaw. But Mr Kaim con­sid­ers the approach to be out­dat­ed under cur­rent cli­mate con­di­tions. “Soil isn’t meant to be bare. It should stay cov­ered to pre­vent it from dry­ing out.” The closed veg­e­ta­tion cov­er also pre­vents rain­drops from hit­ting the soil like a ham­mer, which reduces water runoff: The farmer’s goal is to ensure that the rain will infil­trate in the square metre where it falls.

Sam­ple of min­er­al soil tak­en in an alfal­fa field.

Delay­ing the drought

Under­sown crops have proven to be very use­ful on plots sub­ject to ero­sion. If it rains in autumn, they can even be har­vest­ed. Oth­er­wise, they remain in place until the begin­ning of the veg­e­ta­tive peri­od. In this way, they play their anti-ero­sion role “but don’t take win­ter water,” says Mr Kaim.

Over the past few years he has dis­cussed his approach with col­leagues from the region and com­pared dif­fer­ent sys­tems. Their corn has a bet­ter start than his strip-till corn but the sit­u­a­tion revers­es around mid-June. “Their soil has no more water. Our corn stays good for longer.” Here, col­lect­ing rain in a basin is not an option, but Mr Kaim is con­sid­er­ing build­ing dykes in the for­mer peat bog drainage net­work to stop runoff. “I hope, as a result, to delay the drought by a week. It’s not much, but it’s some­thing.”

How­ev­er, for him, the main adjust­ment vari­able in the face of future droughts remains agron­o­my. “It is essen­tial to pre­serve nat­ur­al water reserves,” he empha­sis­es. The soil is indeed the first tool for stor­ing water.