Potential of Rainwater Harvesting in Dhaka City: An Empirical Study

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Potential of



in Dhaka City:

An Empirical

Dear Fellow-Rainwater harvesters,

While working on something else I just came across a very interesting paper about the potential of rainwater harvesting in Dhaka City. See attached.

The inability of public water facilities to function effectively in Dhaka City has made it impossible for most of the city dwellers to have access to safe water supply. The concept of rainwater harvesting is an economical small-scale technology, which has the potential to boost safe water supply with least disturbance to the environment. Dhaka being a mega city, only limited city dwellers has reasonable access to reliable water supply. This study explores to assess the potential for harvesting of rainwater as an alternative option in Dhaka City, which shows that rainwater can provide significant amount of supply against its demand. There is, therefore, sufficient rainwater to supplement the need of the city dwellers if the arrangement for rainwater harvesting activities could be improved.


- K


Dear Harvesters,

Kerstin has just circulated a useful study in Dhaka on urban RWH - mainly, one might say, urban 'supplementary' RWH.

Bangladesh, whose climate is quite good for RWH despite being Monsoonal, has never really taken to RWH despite its apparent relevance to the national 'arsenic-contamination-of-groundwater' problem. Now the groundwater situation in Dhaka city is getting critical with unacceptable annual falls in the water table. there is also pollution of the plentiful surface water. The very flat landscape for 100km around Dhaka precludes the economical construction of storage for river water, though presumably cleaner river water is available from North of the city.

But big-city RWH is not so easy. The roof area per inhabitant will be low wherever housing height exceeds 2 floors. Locating storage is difficult as it should be below the level of roofing gutters, the building structure may not carry heavy weights on upper floors, ground-level space is scarce and expensive (and storage at or below ground level needs pumping).

Roofwater could be used directly - maybe under legal duress - for aquifer replenishment, as in Mumbai. However harvesting for immediate use would surely be more popular. IF (a big IF) conserving the aquifer is the main issue, then low-cost (small storage) 'wet season' RWH would be attractive. Storage might be as little as 60 litres per person served. For half of each year that could markedly increase water security. The Yeasmin/Rahman paper mentions 'supplementing' the needs of city dwellers, but it's not clear if they mean a seasonal supplement for many or an alternative supply for a few.

However that still leaves the problem of managing the sharing of roofwater in buildings where one roof covers many households. RWH is of all water sources the most difficult to manage, so a formal (commercial?) system of allocation rather than a 'communal' one is almost certainly required. Having a header or 'day' tank in each subscribing household/flat would ease water management and cost-recovery.

There are several large cities in Dhaka's situation, but many (e.g Singapore, Guangzhou) are now building housing so high (over 10 storeys) that the roof area per person is negligible.

- T

Dear Friends, the problem with RWH is that you need a lot of space for storage of water. If there is no space, the chances for RWH are limited. If there is some storage available, clever (foil) and flexible tanks can be used in combination with solar driven UV disinfection. For an example of a foil tank see attached RWH description of project in Walalane, Senegal. Started 3 years ago and still running fine. Dependant on needs the shape of foil tanks can be changed easily.

- M

Picture show RainCAP installation Walalane Senegal aug 2014.pdf

Dear colleagues,

Following email by Kerstin in relation to rainwater harvesting in Bangladesh I wanted to share with you that as part of a recent mission to the country I had the opportunity to visit some low-cost aquifer recharge schemes supported by UNICEF and in collaboration with the University of Dhaka and Acacia Water. This is indeed a climate resilient option to water supply there...

The application of the MAR concept in Bangladesh is simple: water is collected from ponds and roofs (after passing through a sand filter), and then injected into the shallow saline aquifer through a ring of infiltration wells, creating a lens of fresh water. After the turbidity of the water has improved to an acceptable level, water can be abstracted using a standard handpump yielding water of generally improved quality (reduced levels of turbidity, coliforms, iron and arsenic), which is available throughout the year. Each scheme can serve several hundred people and importantly, can be easily maintained by community groups. Of the 20 sites constructed to date, 17[1] are operational, with another 80 sites planned for 2014. Importantly for Bangladesh, the creation of a freshwater lens offers significant flood protection during the regular cyclonic surges and the systems facilitate the provision of safe water when other traditional sources have been damaged by the floods.

Best regards,

- J

UNICEF innovations in
South Asia - Bangladesh

Dear Fellow-Rainwater Harvesters,

While not specifically focused towards urban supply, one recent project initiated and launched with Japanese support through JICA in cooperation with Bangladeshi partners is called Amamizu. At the heart of this project is to encourage the adoption of Thai jars used so successfully in Thailand for RWH in rural Bangladesh. Spearheaded initially by Dr Makoto Murase and others in Japan the project is progressing well and is now well established in Bangladesh where the jars are now being produced commercially.

Amamizu Bangladesh website : http://skywaterbd.com/?page_id=76

Contact in Bangladesh (To view, sign into the D-groups RWH site).

Clearly, RWH in densely populated urban areas presents its own set of challenges (e.g. pollution), but also opportunities (such as economies of scale). Look forward to following further discussions on this and other topics,

Happy harvesting,

- J

Short slide show showing Amamizu’s work in Bangladesh

Dear Fellow-Rainwater Harvesters,

J's relay of the Japanese Amamizu activity in Bangladesh offers some excellent detail, especially concerning Thai jars that are no longer common in Thailand. It seems a good programme. However the Amamizu web site implies the jars hold 1000 litres whereas from the photos they look only about 600 litres. 1000 litre jars (about 1.3m in diameter and height, weighing around 300 kg) are quite difficult to transport, even over flat terrain as in Bangladesh. Bangladeshi (freight) cycle rickshaws can carry several quintals (100 kg) of rice but not on rutted tracks. The original Khon Kaen jars didn't all have taps, so water was dipped out - not so good for either water quality or mosquito-breeding control. The Amamizu workshops are described as 'temporary' - presumably they move to follow the market demand. However having a small production workshop, where cement curing is in the shade and well managed, is a key part of Thai jar quality control. Jar production at the customer's site doesn't work very well - or didn't in a Ugandan programme of 2010.

- T

Dear J,

One of the things that I found particularly striking when I learned about Thailand and its jars (which I understand provide over 30% of the population with drinking water) is that it is not only fulfilling a basic need, nor is it only an industry, but it is also art and hospitality.

As this project in Bangladesh takes off, do you know of whether there has been any face-to-face exchange between these two countries, with government officials, local leaders and private enterprises? This could inspire and ultimately affect millions of lives.

With Bangladesh’s experience of private enterprise selling tubewells, there should be plenty of business-savvy for rainwater harvesting! I watch Bangladesh with baited breath.


- K

Question to M:

Is there anything that speaks against reforesting (food-forest!) the apparent bare land around the foil-tank at the onset of the rainy season? (cultural reasons? too many cattle?)

Contour-line-swales in combination with restoring soil-biology (both inexpensive as long as there is understanding and willingness to do it) could extend rainwater harvesting (*and* -holding) to the whole area, and restore groundwater while yielding food…

- A

Dear all,

I would like to share our,2000 liter capacity Thai-Jar, Rainwater Harvesting tanks with different techniques, which is no need to carry the the whole unit of Thai-Jar from place to place and one mould set can used again and again. It is more easily, just only moved by the iron mould segment (8) pieces, it really effective, and low cost, in our country now, using for household as well as institution. (please see detail in attached my PowerPoint presentation).

Best regards,

- H

Implementing 2000 liter Jars REVIEW-Aug 2014.pptx