[Tellepix]
[Tellepix]

Satellite imagery has confirmed a dramatic drop in water levels at major dams and reservoirs across southern South Korea as a prolonged heat wave and drought grip the region. Some reservoirs have shrunk to the point where their beds are exposed, prompting experts to call for long-term water resource management strategies to address what they describe as a "compound disaster" — the simultaneous occurrence of extreme heat and drought.

Satellite startup Tellepix compared imagery from last year and this year and found that the surface area of Okcheon Reservoir in Changnyeong, South Gyeongsang Province, shrank from 0.129 square kilometers on July 29 last year to 0.014 square kilometers on Aug. 1 this year — a decline of about 88.8 percent, according to Yonhap.

Analysis of imagery from US satellite company Planet showed that most of the reservoir bed had been exposed, with water remaining only in a small stretch near the water intake. The reservoir's storage rate fell from 82.5 percent last year to 11.1 percent over the same period.

As storage rates across South Gyeongsang Province fell sharply, Kim In-jung, president of the Korea Rural Community Corporation, visited Okcheon Reservoir on Tuesday to inspect drought response efforts.

Daegok Dam in Ulsan, which has the lowest storage rate among water-supply dams, also showed a marked reduction in surface area. Its reservoir shrank from 1.268 square kilometers on July 30 last year to 0.566 square kilometers on the same date this year — a 55.4 percent decrease. Satellite images captured wide stretches of exposed riverbed, particularly along upstream tributaries.

Okjeong Lake in Imsil, North Jeolla Province — formed by Seomjingang Dam and a key source of agricultural water for the Honam Plain — was no exception. Its surface area fell from 13.25 square kilometers on Aug. 1 last year to 8.74 square kilometers as of Sunday, a decline of about 34 percent. Tellepix said the shrinkage was especially pronounced along upstream tributaries and in the eastern part of the lake.

Rainfall deficits in the south have also reached a serious level. According to the Korea Meteorological Administration, cumulative precipitation across southern South Korea over the two months through Thursday stood at 212.1 millimeters — just 46.8 percent of the historical average. That is the fourth-lowest figure recorded since the national weather observation network was expanded in 1973.

Soil is drying out rapidly as well. Tellepix analyzed data from NASA's Soil Moisture Active Passive satellite and found that while soil moisture increased in central and northern parts of the country, it declined broadly across the south.

Soil moisture change was measured as a ratio of water volume to total soil volume (cubic meters per cubic meter). Ulsan recorded the largest average decline at -0.1268 m³/m³, followed by South Gyeongsang Province at -0.0983 m³/m³, South Jeolla Province at -0.0489 m³/m³ and North Jeolla Province at -0.0181 m³/m³.

"This summer, southern South Korea has seen rainfall at roughly half the 10-year average, leading to a significant drop in storage rates, water body surface areas and soil moisture — a broad worsening of drought conditions," said Kim Hye-ri, a senior researcher at Tellepix's rapid analysis team. "In particular, Daegok Dam and Okcheon Reservoir have seen storage rates fall to around 10 percent, making continuous monitoring and preparation for water shortages essential."

Experts warn that compound disasters combining heat waves and drought are likely to become more frequent, and that existing response measures alone will not be sufficient.

Yea Sang-wook, a professor at Ewha Womans University, said the drought gripping southern South Korea is a textbook example of a drought-heat wave compound disaster. "When heat waves and drought occur together as a compound disaster, their combined intensity exceeds that of either event in isolation — and so does the damage," he said.

Kuk Jong-sung, a professor at Seoul National University, said the risk of alternating droughts and downpours is growing. "Going forward, we may see longer dry spells punctuated by short, intense bursts of heavy rain," he said. "We need to move beyond short-term forecasts and use seasonal predictions and decades-long climate outlooks to track regional changes in precipitation, rainy days, rainfall intensity and soil moisture — then incorporate that data into long-term national disaster mitigation policy covering dam and reservoir operations, agricultural and industrial water allocation, and urban drainage and retention infrastructure."

Oh Jae-ho, chief executive of Nanoweather and an emeritus professor at Pukyong National University, said climate disasters are not isolated events but cascading compound crises in which heat waves, drought, wildfires and water quality degradation feed into one another. "The dam, water supply, wildfire suppression and disaster warning systems we built around past climate baselines are no longer adequate," he said. "We urgently need to redesign critical infrastructure to reflect current climate risks and adopt a proactive, integrated response."

As climate change drives more extreme and erratic weather, droughts and heavy rains are alternating with increasing frequency. Experts say the central challenge ahead is to move away from simply waiting for rain and instead overhaul reservoir and dam operations, secure agricultural and household water supplies, and restructure disaster response systems to meet the realities of a changing climate.


rainbow@heraldcorp.com