Why does drought happen?

Drought can be catastrophic. For good reason, people refer to times of extreme drought as water crises. Farmers, industries and cities have been brought to their knees by it. But, have you ever asked yourself why does drought happen?

Very simply put, drought happens, because it is part of how the planet works. If you live in a city, it’s not that easy to see it. Here, we have covered most of the earth’s brown and green surfaces with grey. We get water from a tap, so we cannot see the intricate system where it comes from. We do not share our living space with large mammals anymore, while many of the smaller species are kept at a safe distance. 

Yet, in the wilderness, the process of drought is still allowed to play out. The Kruger National Park, the biggest protected area in South Africa, is one such place. What makes drought in Kruger so spectacular, is that it is used as a big laboratory to teach us how the environment functions and takes care of itself.

Drought has long been an intimate part of the history of this incredible place. When you are there, feeling the sun on your face at day; hearing the laugh of hyenas in the distance at night; its almost impossible to remember that cities even exist. So, you might also ask yourself what a blog about Kruger is doing here, on a site dedicated to cities.

Well, first, it teaches us why drought happens. Second, looking at the history of drought in Kruger makes it very clear that it is something that should be planned for. Drought will come again, though the nature and intensity of droughts are changing. Third, you are not as far removed from the wilderness as you think. The same rivers that farmers get water from to irrigate your food, and that mines draw water from to generate power also often run through protected areas. In Kruger the rivers look impossibly serene and beautiful, lined by gigantic trees, and visited by roaming herds of elephants. But, make no mistake, most of these rivers work hard. Many are used, and dirtied, and dammed outside the park, to make life as we know it, happen.

Thus, learning  how they function, and how to keep them functioning when water is scarce, are important things to know.

Now is also a great time to dig up old stories about drought in Kruger. I’ve been writing about it for many years. Many people were keeping a close eye on weather patterns following the 1991/92 drought – waiting for the next one. Signs that this was about to happen came in 2014 and boy, did that drought deliver. It was, literally, one for the record books.

Now, in retrospect, its time to write about what we have learned from this (the 2014/16 drought in Kruger). Before I tell you about that, I’ll tell you about the 91/92 drought. It was, mildly put, a game changer. Consequences still ripple through policy and management plans many decades later.

What causes a drought?

Across the central and eastern Pacific, there is a constant interplay between the temperature of the ocean and the atmosphere. It is referred to as the El Niño-Southern Oscilation (ENSO) cycle. Sometimes, the temperature fluctuates higher or lower than the norm, affecting weather and climate across the globe. Simply put, a cold ocean water phase is referred to as La Niña. A warm phase is known as El Niño. If you live in the southern hemisphere,  El Niño is often mentioned in the same breath as drought.

The El Niño-related droughts of 1982/83 and 1991/92 were the most severe droughts on record in the Kruger park and large parts of the rest of southern Africa.  

During the latter, according to Dr Eddie Riddell, the park’s manager for freshwater resources, the park only received 44% of the long-term average rainfall from a 100-year record. Both those mentioned droughts were characterised by below normal rainfall for two consecutive years. 

To put it into a bit of perspective, the mean annual rainfall in the park  varies from about 740 mm at Pretoriuskop in the south to about 440 mm at Pafuri in the north. During droughts or floods rainfall can vary from 50% below or 50% above the long-term average respectively. Naturally, there are cycles of high and low rainfall. These are like a spoon to stir in all the ingredients necessary for a healthy ecosystem – weak animals die, for example, leaving the strongest to carry the herd forward. 

Extreme drought however, like the caliber of the early 80s and early 90s droughts, are completely different animals.

Extreme drought, extreme impact

These droughts (or extreme floods) can leave the entire ecosystem changed for many years. This is especially the case in conservation areas like Kruger. Though it looks like a wilderness to us, its very much managed. Fences curb the system, and the rivers that run through it are already altered before they enter the park. 

The severe drought of 1991/92 was a perfect example. The impact was near inconceivable to those that have not experienced it before. In March 1992, the Sabie River, generally regarded as the most biodiverse in South Africa, was near to losing its status as a perennial river for the first time in recorded history. It forced major water users in the catchment to come together, eventually forming the Sabie River Working Group (SRWG), consisting of irrigation farmers and forestry and State departments.

Farmers restricted irrigation up to 60% and forestry ringbarked hundreds of stray trees along the banks of the river, preventing the Sabie from drying up. Inside the park, the 30 000 strong buffalo population shrank by about 60% to 14 000 and many other herbivore numbers plummeted. Thousands of hippos, warthogs, common reedbucks, kudus and giraffes died, so did rare antelope such as roan, sable, eland and tsessebe. According to Dr Freek Venter, the park’s conservation general manager at the time, many of these animal populations rebounded in the wet years that followed, though rare antelope numbers remained low.

Preparing for the next drought 

Since then, a number of changes have taken place in the park. The 1991/92 drought was one of the most researched and documented, says Eddie. “We know that these dry periods change the balance in favour of the plains game such as zebra and blue wildebeest who eat the shorter grasses, while not favouring those long grass feeders such as buffalo and the rare roan, tsessebe and reedbuck.” This leads to the composition of grass species to change.

“We also know that the larger predators, such as lion, leopard and hyenas, did well during these times, at the expense of the smaller predators, including wild dog, cheetah and jackal by out-competing them for resources.” Furthermore, the surviving buffalo were the strongest and most resilient, and thus only the ‘best’ re-populated the park.

Large predators, like lions, do well when times are dry. 

Significantly, management started looking differently at the water provision strategy in the park. From 1911 to the 1990s, waterholes were steadily opened, to provide water in an environment that was perceived to be ‘drying out’. As many as 300 were opened. 

Now, water in Kruger is not provided in areas that are naturally dry. Also, waterholes are not spread evenly across the landscape. For the most part, artificial water points were closed down. The theory is that this allows for natural plant and animal distribution patterns. 

You see, a common misconception is that animals die of thirst during long droughts. In fact, most starve to death after the food has been depleted, explains Eddie. Some animal and plant species flourish when plenty of water is provided, while others do not. It is therefore important to provide water in a way that creates conditions suitable for sustaining a wide range of biodiversity, and not only for those species that do better in close proximity to water (like zebra and blue wildebeest).

Thus those species that prefer to occupy drier areas further from water where there are fewer predators, less competition for food and less trampling (like sable and roan antelope) also need to be catered for. The park’s new water provision policy creates refuge areas for grass further away from permanent water. The aim is for seasonal variation in water availability and drought episodes to again fulfill their natural function in the system.  Research already suggests some recovery of the vegetation and animal distribution patterns since waterpoint closures.

Furthermore, our rivers gained the legal right to survive. When the National Water Act of ’98 was passed, it made provision for the Ecological Reserve. This clause determines that water of a certain quantity and quality must be made available to rivers and other waterbodies, by law, to sustain the natural ecosystem.

The next drought thus took place in an environment where conservation principles have changed considerably. 

The questions that remained 

For Kruger management, a number of questions waited for the next drought to be answered. Would the perennial rivers dry up again? Would the more natural distribution of water lessen the drought impact on the vegetation some distance away from permanent water?

Furthermore, what would happen to other rare antelope such as sable, tsessebe, eland and reedbuck? And the elephants? Would their numbers increase or decrease? 

Another drought, another set of lessons  

The 2014/16 drought was again another to break records. This severe drought also saw record numbers of extremely hot days – more than ever (on record) experienced in the park. 

From my inquiries so far, its clear that letting more room for nature to run itself has made the park more resilient to drought than ever before. These findings and results will be posted in a couple of weeks.

So, check back soon, or subscribe here to stay up to date with posts. Or, if you have any thoughts to share in the meantime, get in touch. You can say hello by dropping me a note at petro@50liters.com.

UPDATE: As it turns out, Kruger emerged better than ever before from the 201/16 drought. Have a look at what happened, here.

*By the way, this blog has been chopped and changed from an earlier version that I wrote for the The Water Wheel, published by the Water Research Commission in 2016.

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