Pro IQRA News Updates.
July 2022 was the driest July in England since 1935. Coupled with record-breaking temperatures, we’re talking droughts comparable to the Great Drought of 1976, with threats to disrupt public water supplies and poor crop yields, especially fruits and vegetables. Is. . But not all droughts are the same and not all farmers are affected by the same type of drought.
To meteorologists, drought is generally defined as a period of significantly below-average rainfall. However, even low rainfall throughout the season does not necessarily mean that water supplies will remain low, or that industry or agriculture will suffer, as reservoirs and groundwater may already hold much more water.
Of course, such reserves are of little help to grasslands, cereals and other crops that rely entirely on rainfall and are adversely affected when we have dry spring and summer. The past 12 months have been particularly dry across much of the UK and since May 2021 only October and February have recorded above average rainfall.
The situation is even worse when combined with the high temperatures and abundant sunshine we’ve seen this year, which increases evaporation and depletes soil of water needed for plant growth – the so-called “agricultural drought.” Called “Sally”.
We examined the combined effects of low rainfall and hot, sunny weather using potential soil moisture deficit (PSMD), which measures rainfall input to soil and potential losses through evaporation and plant transpiration. There is an overall measure of balance (in mm) between. .
When evaporation exceeds precipitation, the soil dries out and PSMD increases. It decreases when it rains. Generally, PSMD starts growing in late March or early April, peaking in August or September when the soil is driest. A high PSMD means that rain-fed crops like cereals and grasses will be affected as well as our orchards.
Using data from the Cambridge weather stations, we estimate that the PSMD in 2022 behaves (so far) similar to 1976. The deficit started widening in early March and continued to widen until late July.
This is in contrast to the last drought in 2018, when the spring was wet and soil drying was delayed. PSMD currently stands at around 350mm, which is around 50% higher than the average peak between 1981 and 2010. So for farmers who depend entirely on rain, 2022 looks like it could be as severe an agricultural drought as 1976.
Irrigated farming may be banned.
Most grassland and “broadacre” crops such as cereals and oilseeds are grown without irrigation in the UK. It’s not that they don’t need water, but that investing in irrigation equipment is financially unattractive.
However, to ensure production and especially crop quality, most of the UK’s potato, vegetable and fruit crops are supplied with additional water through irrigation during droughts. Dry soils also mean that water demand for irrigated crops will be higher, competing with less available water resources for other sectors.
To a water resources manager, a “hydrological drought” occurs when the water available in rivers, reservoirs, and groundwater is insufficient to meet demand—including the demand to maintain healthy aquatic ecosystems.
Potatoes account for more than half of the UK’s irrigated area and the volume of irrigation water used. In a dry year, we estimate that one hectare of potatoes (just over half a football pitch) requires more than 2 million liters of irrigation water to maintain yield and quality. Which is more than 40 liters for every kilogram of potato.
As UK irrigated agriculture and horticulture require a lot of water but are considered non-essential consumers, irrigated farmers are at risk of compulsory restrictions during droughts, with potentially severe financial consequences. There are effects.
Here we see the difference between 1976 – the driest since 1975 – and 2022. The Meteorological Department termed the rainfall expected in 2021 as “unremarkable”. In addition, improved water metering and investment in infrastructure to divert water from available areas as needed means that water resources are now in better shape than they were in 1976.
The maps below show the state of river flow across the country in February 1976 and February 2022. Pink to red colors indicate river flows that were below normal (pink) to abnormally low (crimson) for the time of year.
So while this year’s dry and hot weather has been similar to 1976 with similar effects on our gardens and farming, last winter depleted water resources that were normal for most of the year. This means that we do not expect large-scale mandatory restrictions on irrigated fields, although some restrictions may be imposed to protect supplies in certain catchments.
However, although the water resource situation in 2022 is not as dire as it was in 1976, there is a need to manage demand across all uses to prevent a severe hydrological drought this year. It is also wise to manage our water resources carefully in the summer of 2022, not only to avoid restrictions this year, but also to reduce the risk of more severe restrictions next year if the UK experiences a dry winter this dry summer. Acts together.