OVERCONSUMPTION OR CLIMATE CHANGE?

By: Zafrir Rinat

Photo: Haaretz

The question of why the Sea of Galilee, Israel’s only major fresh water lake, has fallen to such low levels in recent years is currently the subject of major debate. Some experts argue that human-induced climate change is behind the area’s five-year drought and the decades-long decline in rainfall in the region.

In an article published in the Journal of Hydrology this week, Israeli researchers examined various models for climate change and compared them to the developments around the Sea of Galilee in recent decades. The authors predict that the flow of water through the Jordan River, the principal source of the Sea of Galilee, which is also known as Lake Kinneret, will decline by 12 to 22 percent or even more over the next century, presenting dramatic implications for the region’s water supply. The paper was written by two researchers from the Israel Water Authority, Dror Paz and Amir Givati, together with Prof. Daniel Rosenfeld of the Hebrew University of Jerusalem and French researcher Guillaume Thirel.

But other Israeli researchers proposed a different explanation in the journal Science of the Total Environment. They found that the amount of water reaching the headwaters of the Jordan River hasn’t declined significantly, nor has Lebanon significantly increased its consumption from the headwaters. They have therefore concluded that the drop in the amount of water reaching the Kinneret must be due to increased consumption in Israel, primarily for agricultural purposes. Climate change alone can’t explain the fall in the Kinneret’s water level, said these researchers, Michael Wine and Jonathan Laronne of Ben-Gurion University of the Negev and Alon Rimmer of the Kinneret Limnological Laboratory. Without human intervention, they claimed, its level would have remained stable despite the drought of the past few years.

Moreover, they said, if consumption of water from the Kinneret’s drainage basin were to be reduced, the water level would rise and stabilize at its upper limit, enabling the flow of water into the lower parts of the Jordan River to resume within a few years. But the Water Authority has rejected this conclusion.

One of its experts, Amir Givati, published a short response in Science of the Total Environment stating that the conclusion was based on speculations and simulations, not on actual water consumption data. The actual data shows exactly the opposite, that there has been a sharp decline in the amount of rainfall. And this, not increased agricultural consumption, explains the decreased flow of water into the Sea of Galilee, Givati insisted.

The falling water level has prompted concern that the quality of the Kinneret’s water will suffer. But for his part, Prof. Moshe Gofen, who has studied the Kinneret basin for years, said there is no direct, clear connection between lower water levels and the water’s quality.

One of the most far-reaching ecological changes in the lake, he noted, has been in its levels of two fertilizer agents, phosphorus and nitrogen. This has resulted in the disappearance of the lake’s characteristic algae, called peridinium, and the appearance of bacteria that can harm water quality. Yet these changes took place 25 years ago, when the level of the lake was still high. Studies show that the lake’s water level has undergone radical changes for various reasons over the past 9,000 years, Gofen said, but the lake has survived.

Nevertheless, there is a direct link between drought and salinity, which also affects water quality. The concentration of salt in the Kinneret has risen as the influx of water from rivers and streams, which are less salty, has fallen. Natural evaporation from the lake is increasing its salinity further, threatening to make the water unusable.

Gofen has argued that, given this situation, as much salty lake water as possible should be replaced with fresh water from streams, even if this temporarily lowers the Kinneret’s level even further. In addition, the Water Authority has already begun diverting water from salty springs away from the lake.

The challenge is to preserve the Sea of Galilee as a source of water for humans while also preserving it as an ecosystem that includes springs and streams. If the quantity of rainfall indeed continues to decline due to climate change, and if the region’s population grows as predicted, it will be necessary to take active steps to alleviate the lake’s problems. One such step is already being taken. Water is being sent to the lake through the National Water Carrier from other parts of the country that have been less affected by the drought thanks to desalination.