Day 02: Thematic Session 01
Best practices in different hydro-geological contexts focusing recharge of ground water and reuse of rainwater.
Bangladesh Convention on Rainwater Harvesting
Hotel Ruposhi Bangla, Dhaka,
15 to 17 June 2012
The theme of this parallel session was ‘Best practice in different hydro-geological contexts focusing recharge of groundwater and reuse of rainwater’. The chairperson and moderator was Dr. Suresh Kumar Rohilla.
The paper presenter were: Kazi Rashed Hyder (Low cost RWH system: Context specific, user friendly and affordable), Dr. Md. Mafizur Rahman (Potential of using stored RW for long period to reduce drinking water crisis through RWH), Ms Salma A Shafi (Rain water collection for domestic use: A solution for water supply to urban low income communities). Following are the deliberations:
Paper 1: Low cost RWH system: Context specific, user friendly and affordable by Kazi Rashed Hyder
In his presentation he focused on hydro-geological contexts of coastal areas where he pointed out the following facts i.e. Limited safe water sources, Shallow aquifer -high levels of saline and arsenic, Deep aquifer is not available (in many areas), Surface water supplies are threatened by saline intrusion, Poor people live in remotely scattered places. In the presentation, the presenter described the scenario of the coastal areas on safe water and domestic water supply scenario in the Aila affected coastal areas. In the presentation he focused on the activities of WaterAid in coastal areas since 2006 which are:
- working in three upazilas (Syamnagar, Assasuni, Koira) and Paikgacha Municipality
- installed safe water facilities (Shallow Hand Tube-well, Deep Hand Tube-well, Pond Sand Filter, Rainwater harvesting Systems, Solar power generated MPWSS)
In the presentation he showed the low cost rain water harvesting system and explained that it was a very simple technology where it needed i. one large poly-fabric sheet (15’X12’) and ii. Four 200 liter capacity clay jars. The total cost is about 2,500 BDT (Poly-fabric sheet 1400 BDT, four clay jars 1100 BDT)
Strengths: Clay jar has always been used traditionally used for water/grain storage and it is locally available and user friendly. It is also low-cost & transportable. The poly fabric sheet can be easily fixed on rooftops or courtyards, it stops rain trickling through thatched roof and water is cool, covered. The O&M cost is low and it can be used if households are scattered.
Challenges: Clay jars are difficult to transport, needs regular cleaning and must be well maintained.
Open discussion: In the open discussion session, the participants asked the following questions:
1. What is the cleaning process of clay jar?
Rashed Hyder replied that the clay pot should be covered properly. It should be maintained and should be cleaned with straws.
2. What will be the cost of the jar?
In response to that question he replied that it will cost 215 tk per jar in terms of 200 litre jar and the total cost will be 2500 including everything.
3. In terms of saline silt ponds how far this project is successful?
Rashed Hyder said that it is better to avoid saline silt ponds but OXFAM was successful in Munshiganj regarding this issue.
4. One of the questions was that who was paying for the clay jar?
In response to this question, he said that WaterAid is paying the cost on behalf of the users.
Paper 2: Rainwater harvesting and Its long term storage for drinking in coastal rural areas of Bangladesh considering adaptive capability and available resource by Maharam Dakua on behalf of Dr. Md. Mafizur Rahman
The presentation focused on the crisis of fresh water. He explained that earth has a limited supply of fresh water stored in aquifers, surface waters and the atmosphere. The water security is pandemic and is a shared threat to human and nature.
The important and mostly used water supply technologies used in the rural and semi-urban areas of Bangladesh include:
- Shallow shrouded tube well (SST) and Very shallow shrouded tube well (VSST)
- Deep Tube well;
- Dug Well;
- Pond Sand Filter (PSF);
- Protected Ponds;
- Household Filters; and
- Rainwater Harvesting
Combinations of high water table and salt water intrusion (through river and disasters) have left the mostly used options redundant in many of the coastal areas. High maintenance requirement, operational complexity and lack of efficiency make some other technologies/ processes not acceptable to people. In an attempt to explore the suitable options in the context of accessibility and quality, a survey was conducted in Mongla of Bagerhat district, which is one of the most vulnerable areas to climate change. The main findings of the study was that people, with the ability to install the rainwater storage tank by their own are storing and using the rainwater. The rest of the people are spending their money and time to collect water from distant places, although the quality of that water is highly questionable.
Considering the ongoing crisis and demand of low-income group in the coastal region, ITN-BUET decided to install Rainwater Harvesting System for 20 families under EC-CAFOD funded IFLS project. ITN-BUET provided training to the beneficiaries on operation and maintenance. The prime objective of the research was i. Rainwater harvesting is a suitable solution in the coastal areas of Bangladesh considering the cost and other alternate solutions. ii. To show that sound maintenance and operation of rainwater harvesting system can protect stored rainwater from microbial health risks.
From observations, more than 70% families with income less than US$150 per month are not happy with the current water sources, though were found paying 3-7% of their monthly income for buying this water. From the random observations, it was calculated that people in villages of Mongla are spending around Tk. 400 to 600 for buying water from distant places which include the cost of water and fuel cost of travelling. The income level was below Tk. 10,000 for 70% of the respondent in that area and this income level group was found spending around 5-20 % of their monthly income for water.
Rainwater Harvesting as a Solution
• The cost of ITN-BUET constructed reinforced tank for 10 families = 80,000 BDT
• Estimating the total expenditure of all 10 families per year = (600 x 10 x 6) = 36,000 BDT (considering 6 months; remaining 6 months during rain they store rainwater in pots and jars)
• The return period of initial investment is less than 2.5 years!
Perception: is rainwater good enough for long term storage?
• The quality of rainwater is comparatively good as it is valued for its purity and softness, has a nearly neutral pH, and is free from disinfection by-products, salts, minerals and other natural and man-made contaminants before collection.
• Higher microbial concentrations are generally found in the first flush of rainwater, but the level of contamination reduces as the rain continues.
• But the familiar perception among many of us that rainwater is only good enough for a few days and rainwater quality getting deteriorated with time have been a major obstacle for using this abundant source of fresh water till now.
Rainwater Harvesting: Health Risks
Poor hygiene in storing water and abstracting from tanks or at the point of use cause contamination and pose health concerns. However, risks from these hazards can be minimized by good design and practice during operation and maintenance.
Long Term Storage of Rainwater
There are issues around maintenance of RWH. These are:
- At least once a year cleaning and disinfecting the inside of the storage tank
- Keeping the catchment clean.
- Washing the filter regularly to avoid clogging.
- Avoid first few minutes of rainfall
- Protect the tank from any type of external contamination i.e. do not extract water from inside using bucket.
This research recommends to promote the practice of rainwater storage by proper maintenance for long period to help reduce the crisis in areas where drinking water is scarce. Finally the presentation came to an end by stating that considering the other available options (PSF, RO, piped water supply coverage etc), the decision makers of Bangladesh should opt for properly planned and designed Rainwater Harvesting System which will:
- Ensure safe drinking water (also for other parts of Bangladesh)
- Be sustainable and cost effective in the long run considering adaptive capability and available resources.
Open discussion: In the open discussion the participants asked the following questions:
1. In terms of maintaining rainwater for so long, was there any kind of practical experience?
In response to the question presenter said that the information was based on practical experience. ITN-Buet conducted research on two tanks very carefully.
2. Another question was, how did the family share water equally?
In response to the question the presenter replied that there was a treaty between the 10 families that they will use water 2.4 litre per day in a regulated way.
3. What is the size of the tank and how many tests were performed?
Presenter replied that each tank has the capacity of holding 10500 liters of water and the testing frequency is 1 month.
4. Is there any test result of traditionally collected rainwater?
In response to that question, the presenter replied that they don’t have any test result of that.
5. What is the maintaining cost of the tank?
Presenter replied that Tk 80000 covered all the expenses including maintenance.
Paper 3: Rain Water Collection for Domestic Use: A Solution for Water Supply to Urban Low Income Communities by Salma A. Shafi
Rainwater harvesting and storage is not a new technology. It has been used for domestic and agricultural uses for a long time in different parts of the world. However, rainwater harvesting is not a common practice in Bangladesh. Only 35.5 percent households have been found to use rainwater as a source of drinking water during the rainy seasons in coastal areas where there is a problem of high salinity. Also, in the backdrop of arsenic contamination in groundwater of Bangladesh, rainwater can be considered as a potential source of arsenic free water. In this paper the author explores the possibility of rain water collection and use in slum and squatter areas of Dhaka and other cities. The presentation focused on:
Roofing materials in Bangladesh: Different types of roofing materials are used in Bangladesh. These include cement concrete, tiles, C.I./metal sheet, and straw with or without polythene covering and bamboo with polythene covering. According to the Bangladesh Bureau of Statistics (1995), about 48% households in the urban area have tiles, C.I./metal sheet as roofing materials. These roofing materials are suitable for rainwater catchment.
Features of rain water collection: The two major components in rain water harvesting system are the catchment and the storage. Most commonly ‘roof tops’ are used as the catchment.
Estimated water need and consumption: Storing the collected rain water in one 2000 liters capacity jar or two 1000 liters capacity jars can meet the requirement of a family during dry season.
Cost for a 1,000 liters jar is Tk. 2500.00, 2000 liters jar is Tk. 3,000.00 and 3200 liters tank (Segmental tank) is Tk. 6,000.00. Then the presentation focused on segmental tank. The segmental tank has a cylindrical shape. It is built by an assembly of precast cement segments composed of a mixture of cement and sand. Its inner and outer side is cement paved and its lid is cement precast. The tank is much easier to assemble than that of steel frame and can be built in a large quantity at a time. It costs about Tk. 6,000.00 and the storage capacity is about 3200 liters.
The presenter also discussed that roof catchment tanks can provide good quality rain water; clean enough for anyone to drink so long as:
• A clean impervious roof made from nontoxic material is used (lead paints and asbestos roofs ‘should be avoided’)
• Roofs should also be free from over hanging trees since birds and animals in the trees may defecate on the roof.
The presentation also dealt with the detail constructions of the jars/tanks, economic and social and technical considerations. The presentation also discussed about the strategy to introduced rain water collection among the urban poor in Dhaka city.
Open discussion: In the open discussion the participants asked the following question:
1. If rainwater harvesting system is done in slum areas, what will be the consequences as slum areas could be evicted anytime?
In response to this question presenter replied that most of the slum areas are situated in private lands. Therefore they will not be evicted.
2. Another question was whether public toilets have these kinds of rainwater harvesting system?
In response to the question presenter said that there are water collection systems in public toilet but those water are for non-drinking purpose only.
Moderator concluded the session by thanking the presenter for their informative and interesting presentation and thanked the participants for their active participation.