The economics of harvesting rain


More than ever before, Tanzania and the rest of Africa need to employ rain harvesting technology. Global climate changing is drastically affecting weather patterns, rains are heavier or missing completely, droughts in otherwise tropical areas, cyclones and tornadoes ravaging through coastlines. Weather is now less predictable than ever before.

For both economic and social reasons, Tanzania needs to make the best of the rains when they come, Tanzania needs to harvest rain water.

While at national or even city levels, there are some sophisticated equations involved in rain harvesting, like building reservoirs and purification sites, but all in all, the science of rain harvesting technology is not all that complicated at all. It’s a simple three step investment, collect, store and purify.

Since economies rely on water for production and households depend on clean and safe water for daily survivor, harvesting rain water should not even be optional, it should be a legal matter. That’s right, there ought to be a law that requires every house and even commercial building to have gutters and reservoirs. Why?

A common ironic challenge for Tanzania is that even when the rains come, the country continues to suffer dire shortage of clean and safe water. Worse still, even water for irrigation is a problem despite the economy’s reliance on agriculture.

As all tropical East African countries, Tanzania could take advantage of its two rainfall peaks and use them to collect, purify and store clean and safe water for both domestic and commercial use.

But no, instead of filling large reservoirs come the rains, Tanzania literally goes into a stand still. Roads are closed, busses and trains stop operating, flooding everywhere. This bi-annual travesty could be turned around into an opportunity, economic solution.

With rain harvesting technology, Tanzania could easily turn the flooding problem into a solution for access to safe reliable water source all year long.

Let’s start with individual households. Each and every house should create a home rain harvesting system. It does not involve much, simple inexpensive three steps, collect, store, purify.

Political will: Subsidize gutters, storage tanks

Let’s start with the collection. Most houses in Tanzania are roofed with variations of corrugated iron sheets, tiles and in the villages thatched grass roofing. So collection involves setting up a gutter system on each house, and I propose this should be a legal mandatory task.

There various options to gutters. Metal alloys and casted plastic gutters are the commonest options and are probably the most expensive. This is where political will comes in. Just like there is need for a law to enforce harvesting rain water, there should be subsidise for both imports and local production.

Here rises another economic opportunity that for Tanzania, should be incentive enough to  push the bill through parliament without much hustle. The country’s national development plan that is meant to ferry the country from low to middle income status is hinged on industrialization.

Local production of plastic and metal gutters requires establishment of small manufacturing industries. Set up of these medium sized plants will also create numerous jobs and earn the government tax revenue in the process.

Second is the storage aspect. This is also a simple step that has huge multiplier effect to the economy. For storage, heavy duty tanks are required, the kind that are already dotted on many housing complexes across the country.

However, while plastic tanks are widely used in the country, they are in very few cases used to harvest rain water. They are mostly filled using regular tap water, they serve as storage for when tap water stops running, which is all too frequent. In effect, the tanks are actually evidence of the country’s water problems.

Making it mandatory for each house to have a water storage facility with a capacity of at least 2000 litres will in effect increase their production. Yes you got it right, that will again roll out the multiplier effect, more production facilities, more jobs, more revenue.

However, the public is likely to resist any law forcing you to spend more than you had planned. However, political will comes in play again by subsidizing these tanks and even bringing in financiers as middlemen to bridge the cash gap.

That is, the financiers foot the bill, the recipients pay back in instalments that they are comfortable with, plus a small charge for the service.

There are also various options to the water storage question. It could be a shared investment for every few houses. Take for instance the rental situation in the slums. You do not expect single roomed houses, of one to three occupants to purchase a water tank.

However, the government can enforce all landlords to install the water tanks and/or since Tanzania already has a 10 house communal system, where occupants of every 10 houses are under one leadership, then every block of 10 houses can share a single water tank etc

Even the tanks themselves have various options, instead of plastic tanks, concrete and clay tanks can be constructed.

Finally comes the last step, purification. Both storage and purification can be complex and expensive at city levels but they are very simple and inexpensive at the household level. There are water filtration and purification system that are commercially available and these too would in this case be subsidised.

Filtration systems can also be easily hand built with regularly available materials like stones and sand. On the other hand purification can be done with simple drop of purification pills or liquids into the water tank. These are safe, inexpensive and readily available.

The same steps are applicable for commercial complexes. In fact, these offer wider areas for water collection because they have larger roofs. They also have larger financial capacity to handle the set up and more importantly, they have the greater need to cut operating costs, and water bills can be daunting.

For businesses, the government should enforce it as part of their sustainability requirements which covers reduced power use, recycling and use of renewable energy. Nothing says, sustainability like harvesting and reusing rain water.


Solving Tanzania’s water problems

At city and national levels, the country’s infrastructure should accommodate the huge amount of water runoff during rain seasons. It is the lack of proper drainage that causes flooding in the cities.

Drainage system should not run to the ocean or other natural water bodies, they should be directed to water purification facilities ready to be re-channelled for domestic and commercial purposes.

In the villages, the rule should be the same, gutters for every house and drainage channels for water runoff and river flooding, also to be channelled to a purification facility. The economic benefit of this investment is immense from job creation to industrializing the country, from health benefits to food security.

AT the home level, by installing simple domestic rain harvesting technology, then, instead of jumping a puddle of water at your door step and navigating water pools in your driveway, you would have clean and safe water collected and purified for home use.

The collected rain water would reduce pressure on the city supplies and also cut your monthly expenses on water bills as well, its a win-win situation.

Worth taking extra precaution on is the purification step. While there are several methods eliminate disease-causing microorganisms in water, chlorination is the most commonly used and is effective against many pathogenic bacteria.

There is the question of dust and other trash on the roof tops but this can be overcome by simple filtration devices in the gutters and in the water tank as well. When combined with filtration, chlorination is an excellent way to disinfect drinking water.

Furthermore, the public should be educated on how to test the quality of drinking water, how to calculate the amount of chlorine needed in a particular situation, by-products of disinfection, and alternative disinfection methods.

Also, if you have a small kitchen garden where you grow vegetables for home use (a food security initiative that I think should also be mandatory for every household) the harvested rain water can serve to irrigate your small garden guaranteeing your family a steady supply of healthy, nutritious, home grown vegetables all year round.

So by establishing this cost effective system to harvest rain water, we can effectively end the ever persistent water shortage that now cripples the country.







Giza Mdoe is an experienced journalist with 10 plus years. He's been a Creative Director on various brand awareness campaigns and a former Copy Editor for some of Tanzania's leading newspapers. He's a graduate with a BA in Journalism from the University of San Jose.

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