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Weather office: 'Be prepared for the worst as far as drought is concerned'

May 18, 2020
Weather office: 'Be prepared for the worst as far as drought is concerned'

Port Elizabeth - The Port Elizabeth office of the South African Weather Service on Monday provided a comprehensive picture of the water and drought situation facing the Nelson Mandela Bay and Kouga municipalities.

"After warnings that the NMBMM could fast be approaching Day Zero, as far as the water crisis is concerned, the question on everybody’s lips is 'When is it going to rain?' or 'What is the Seasonal outlook?', as if this is the magical formula to solve the water crisis in this region," said Garth Sampson, SA Weather Service Client Liaison Officer (Eastern Cape).

"From the outset we must realise that, considering historic and existing weather patterns, rainfall alone is not going to change the situation. That is excluding the doom forecast by the advocates of climate change.

"We are presently in the middle of a water crisis, which will not be solved by one day, month or season’s rainfall."

Sampson said that at this point we must note that a water crisis (water scarcity) is considered as the lack of freshwater resources to meet water demand.

"All sectors of the population are quick to point fingers at the parties that they believe are putting an extra demand on this scarce resource. However, ultimately it is an increase in the population growth rate that is putting more demands on industry and agriculture, thus in turn putting more demand on the available water supply," he explained.

"The water supply is finite with climatic fluctuations. As was highlighted in Biblical times, there are seven years of great abundance followed by seven lean years (famine). This is an adage advocated by farmers for centuries. However, it does hold ground meteorologically.

"There are generally 7 years between a peak and a trough in all weather elements. That is why a climate norm is always taken over 30 years to have 2 peaks and troughs in its calculations."

The NMBMM gets most of its water from the Langkloof catchment, which feeds the Impofu and Churchill Dams, as well as the Patensie/Baviaans catchment which feeds the mighty Kouga Dam.

"The rainfall for these regions is between 450 and 600 mm. So why build a dam in such a dry region?" Sampson asked.

"That is a good question if you want to believe that these people did not really know what they were doing, or there has now been a drastic change in rainfall patterns. One would be extremely naïve to consider this.

"I have always claimed, as far as rainfall is concerned, the abnormal is the normal for this region. We are either at a point where we are experiencing too much rain or too little rain. The settlers discovered this, and the first written account of weather was in 1823 when it was stated that 'Settlers farms were flooded after a prolonged drought'.

"This has continued throughout history and has been documented accordingly. Droughts and floods are thus an integral part of the history of this region." 

Defining drought

He said that it is at this point that the concept of drought must be fully understood.

"The term is very loosely used and most people have the incorrect interpretation of the concept. According to Professor Mike Muller, Climate Specialists, Hydrologists and Disaster Management Specialists generally distinguish between three different types of drought, namely Meteorological, Agricultural and Hydrological Droughts," Sampson said.

"A meteorological drought occurs when the rainfall is less than the average rainfall, for a significant period.

"An agricultural drought occurs when a lack of rainfall leads to a decline in soil moisture affecting pastures and rain-fed crops.

"A hydrological drought occurs when a meteorological drought significantly reduces the availability of water resources in rivers, lakes, dams and even underground water.

"To put it into perspective, one can have small amounts of rainfall at regular intervals that maintain soil moisture at a favourable level so that the pastures and fields are lush and green. This is what many of the old people incorrectly refer to as a Green Drought. However, a true green drought occurs in wintertime where there is green cover, but no actual growth coming from desirable pasture species. A lot of what is seen is weeds that have little value."

Sampson added that, be that as it may, in this so-called Green Drought, there is not enough rainfall falling at one time to cause significant runoff to fill rivers, dams and lakes.

"The opposite would thus be true if we experience a massive flood that fills rivers, dams and lakes, but there is no regular rainfall to maintain soil moisture and thus green pastures," he described.

"That is the norm in most regions, however with the low average rainfall of the NMBMM catchment area, the metro and surrounds cannot rely on 'NORMAL' or even 'ABOVE NORMAL' rainfall to fill its dams.

"In a nutshell we require regular 'mini-floods' over our catchment followed up by regular follow up rains in the form of heavy showers. When we talk about 'mini-floods' we are talking of falls of more than 50 mm in 24 hours over most of the catchment. Studies show that anything less than the magical 50 mm ark makes no significant difference to dam levels. Follow up rains must be in the form of events of 10 mm or more, to provide some run off."

Sampson further said that over this region the weather system responsible for this, in 99% of cases is a cut-off low in the upper atmosphere, or a severe thunderstorm.

"Naturally the cut-off low must be perfectly positioned and accompanied by the necessary surface conditions. This was responsible for the Great 1902 Flood, the Face Changing 1968 Flood and the Devastation 1981 Flood," he said.

"Although these were the major unforgettable floods, there were many smaller ones that never made national and international news. Here we can refer to the 2006 Floods and even the constant barrage of rain in 2012, making it one of the years with the highest rainfall, without a major flood.

"The 50 mm producing system has over the last 25 years produced on average 1.9 events per year. The peak was in 2012 when we had 7 such events, which caused our dams to almost continuously overflow. However, since November 2017, we have not had ONE 50 mm event.

"September 2018 gave us a lifeline with a 40 mm events, but since then there have been no significant falls to create enough runoff to get rivers flowing strong enough to make a marked increase in dam levels."

A hot Summer plus a COVID-19 pandemic

Sampson added that of late, we have seen a record hot summer season, increasing evaporation levels and an increased demand on water, caused amongst other by the COVID-19 pandemic.

"This has caused the water usage to increase to 300 megalitres (ML) per day, up from a figure of 250 ML (what should be used per day). This has caused dam levels to drop drastically to a level fast approaching 20% of total capacity. This has caused alarm bells to go off in some political quarters, where they are aware that the last few percent of capacity is dead capacity," he explained.

"The big question is thus what is the outlook for the rest of the year?

"The seasonal forecast, that has been spot on for the last three years shows a tendency towards normal to above normal rainfall for the autumn winter months. However, this has not been the case thus far in 2020. Considering that winter is the time of year we receive most of our rainfall at a rate of around 50 mm per month, the 14 mm in April and 24 thus far in May is far below the norm.

"The outlook for the next week is also looking bleak, which is even more cause for concern."

He added; "One would then tend to doubt the reliability of the seasonal forecast. However, one must note that the seasonal forecast works in a three-month cycle, moving on one month for each cycle, i.e. March/April /May, Then April/May/June and then May/June/ July.

"Hence the forecast is for the TOTAL rainfall over that period. Thus, for the seasonal forecast to be correct, we would have to have a single or few large events before the end of each period. Each day without rain means that the event must be larger for the forecast to be correct.

"Without being a prophet of doom or spreading false hope, history shows us that one must always be vigilant that during drought times we must prepare for an extreme event in the form of a flood. Add to that any belief in the advocates of climate change, that extreme events will be worse, makes a real recipe for disaster.

"Thus, we must realise that we are going to have a flood that will TEMPORARILY break this drought. Exactly when is the million-dollar question." 

So, what then is the advice to the public?

"Be prepared for the worst as far as the drought is concerned and use water very sparingly as if day-zero will occur next week. However, continue to peruse safe hygiene practices, considering the threat of the COVID-19 pandemic," said Sampson.

"Be aware that a flood WILL occur some time in the future and be prepared. Make sure all obstructions that can cause damming and restrict the free flow of water are removed.

"Constantly listen to the weather forecast and when you hear of an approaching system that could yield good falls, ensure that all gutters are cleaned of leaves and debris. The same applies to drains near your house, this can be done by informing your ward councillor.

"Finally, when that extreme event has occurred, the drought TEMPORARY broken and water restrictions lifted, start preparing for the next water crisis. For example, buy more tanks in the times of abundance when they are cheap."

He said that as the advocates of climate change say, extreme events will be worse, therefore the next drought could be even worse.

"Finally, considering that with the limited/finite resource of water and the ever-increasing demand on it, without a MAJOR increase in the amount of available stored water, the water crisis is not likely to be permanently solved in the near or even distant future. So, use every drop of water sparingly."

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