Precipitation: a focus on climate change

Mauritius is currently facing a meteorological and hydrological drought. Intervening rains are not enough to fill our reservoirs. Why is precipitation still low and what are the factors behind this phenomenon? Experts believe.

Prithviraj Booneeady is acting station manager of Vacoas. He explains that a meteorological drought is characterized by a prolonged absence of precipitation. Hydrological drought occurs when surface and underground water resources are below normal.

Damage from August 2022

“Now we are in a state of meteorological and hydrological drought. With almost dry reservoirs, we have recorded a rainfall deficit since August 2022,” he said. Prithviraj Booneeady points to the latest report of the Intergovernmental Panel on Climate Change (IPCC) released this year. This document talks about the increase in extreme events associated with climate change. As one of the smaller islands, Mauritius will be more exposed to extreme events such as prolonged drought with rainfall below the seasonal average.

There are no cyclones

Hydrologist Farouk Movlabakus also talks about how climate change is causing extreme conditions, including drought and reduced rainfall. “We haven’t had any major cyclones in the last 20 years, let alone the systems that passed by Mauritius. “It is cyclones that bring heavy rains to water reservoirs.”
The recent rains are not enough. “It should rain for at least three days and there should be flow to increase the rate of filling of reservoirs. We can get 130mm of rain in one place in 24 hours like recently, but that doesn’t mean things are going to get any better. The water goes to the sea,” says the hydrologist. The latter adds that it is also a fact that the “rainfall pattern” has changed.

8% reduction

Environmental engineer Vassen Kauppaymuthoo argues that precipitation varies with the seasons of the year. “Meteorological services have found that between 1950 and 2000, rainfall has decreased by 8% over the long term due to climate change. The situation caused by climate change not only at the atmospheric level, but also by the oceans, which now store a large amount of heat, reaches such an extent that today we are talking about heat waves of the oceans (like heat waves on the earth)” supports our interlocutor. These heat waves cause a change in the global ocean circulation and the oceanic dipole of the Indian Ocean, which is equivalent to the El Nino and La Nina climate events in the Pacific Ocean. “This pendulum phenomenon, in which the temperature of the ocean water is warmer on one side of the basin and colder on the other side, causes drought on one side of the Indian Ocean and torrential rains on the other side. This system will also affect the formation and path of cyclones in our region.”

Vassen Kauppaymuthoo adds that these are complex phenomena that are only beginning to be understood. They are still the subject of various studies, because climatology and oceanography are complex sciences. These require the complex integration of a phenomenal amount of, sometimes disparate, information. As an example, he mentions the phenomenon of the formation and development of clouds. This phenomenon is so complex that it cannot be modeled even by the world’s most powerful computers. In this case, it is about modeling the atmosphere (including clouds), the oceans, and the interaction between the two.

Preparation

“The Hydromet project led by the Indian Ocean Commission (IOC) will begin to address this difficult problem and it is hoped that it will gain further insight. This will allow us to measure and warn/predict droughts or torrential rains in advance, so we will be better prepared,” said the environmental engineer. It is clear to him that we cannot fix declining rainfall or torrential rains. “You have to understand that today “With climate change, we find ourselves in situations where one part of the island is under water and the other part is in the sun after a long drought. Tuesday 10th January saw 124mm of rain in Plaisance, 5mm in Albion and just 18mm in Mare-aux-Vacois.” .

Vassen Kauppaymuthoo emphasizes that the world is changing and we must be prepared to deal with natural disasters. Various measures should be taken, including:

  • Increase stormwater capture and storage at the individual and CWA level.
  • Fighting illegal relationships.
  • Repair defective pipes.

“However, this work cannot be carried out without the contribution of all and without comprehensive, integrated thinking, including all actors, as well as various skills”, – our interlocutor believes.

He states that we will have to think and commit to a long-term perspective. “Unfortunately, the droughts of 1961, 1980 and 1998 were soon forgotten after the rains returned. Will this scenario repeat itself in 2023? Will we solve the real problems? Only time will tell,” he concluded.

Water management was criticized

Environmental engineer Vassen Kauppaymuthoo explains that from 1971 to 2000, the average rainfall in Mauritius was about 2,000 mm per year, which means an average of more than two meters of water falls on the entire island of Mauritius (1,865 square kilometers) per year. “This creates a huge volume of water: 1,865 square kilometers x 2 meters of water height, or more than 3,730 million cubic meters of water that irrigates our island every year. Part of this water evaporates (30% or 1119 million cubic meters). ), and the rest seeps into the soil to feed groundwater aquifers (10% or 373 million cubic meters), he explains.

He continues that the amount of available water is therefore the water that feeds the runoff and groundwater aquifers, which is 2,611 million cubic meters. However, according to him, the Central Water Administration (CWA) produces only 300 million cubic meters of water and collects less than 11 percent of this water. “According to the available figures, 180 million cubic meters (60%) of these 300 million cubic meters disappear into nature in the form of leakage or illegal compounds”, – our interlocutor believes.

According to him, if we take into account that the population of Mauritius with a population of 1.2 million consumes 180 liters of water on average per day, we should add about 50,000 tourists in our territory at a given time, which means 225,000 cubic meters of water consumption. meters or 82 million per year. Agriculture consumes about the same amount, but the water returns to the soil through percolation.

“Our water consumption is about 2% of the water that falls on Mauritius every year and 3% of the water is usable in Mauritius (stream and groundwater). “When you see this percentage, you quickly understand that the problem is not with rain, but with the water management system.”

It compares to Dubai with rainfall varying between 140mm and 200mm per year, or 10% of the rainfall in Mauritius. For him, there is no shortage of water in Mauritius.

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