Day 02: Thematic Session 02

Day 02: Thematic Session 02

Rainwater Harvesting in Urban areas, coastal belts,drought prone hilly areas and water logged parts of the city.Bangladesh Convention on Rainwater Harvesting
Hotel Ruposhi Bangla, Dhaka,
15 to 17 June 2012

Introduction

The theme of the parallel session was ‘Rainwater harvesting in urban areas, coastal belts, drought prone hilly areas and water logged parts of city’. Mr.Prakash Amatya from Nepal acted as the modrator and chairperson.

The paper presenters were: Sohail Nazir (Tharparker Desert Rainwater Harvesting initiative), Hasin Jahan (Urban Rain water Harvesting from Bangladesh: Experience, potentials and Challenges) and Kazi Matin Ahmed (Water quality improvement in Coastal aquifers of Khulna Satkhira regions of Bangladesh through managed aquifer recharge: site testing result).

Paper 1: Community Managed Rainwater Harvesting in Tharparker by Sohail Nazir

The drought prone Tharparker Desert in Sindh, Pakistan is the most water-scarce area where livelihoods of 1 million people depend on rain-fed agriculture and livestock rearing. Learning from the sector experiences, NGO Sukaar Foundation has been striving to promote the initiatives of rainwater harvesting in villages of Thar to cope with the issue of water scarcity. As, RWH is an age-old system of collection of rainwater for future use but systematic collection and recharging of ground water, is a recent development and is gaining importance as one of the most feasible and easy to implement remedy to restore the hydrological imbalance and prevent the crisis in areas like Tharparker. Other reasons for increased interest in RWH also include: (1) the shift towards more community-based approaches and technologies which emphasis participation, ownership and sustainability; (2) the increased use of small-scale water supply for productive and economic purposes (livelihoods approach); (3) the decrease in the quality and quantity of ground- and surface water; (4) the failure of many piped water supply systems due to poor O&M and (5) the flexibility and adaptability of rainwater harvesting technology.

The average annual rainfall in Thar Desert area is 350mm. People here are conventionally harvesting 0.06% of total annual rainfall only enough to meet their one fourth of yearly drinking water needs. Sukaar estimates that by harvesting 0.25% of total annual rainfall will maximize current rainwater harvesting capacity by three times – this could enable people to meet their drinking water needs. Moreover, by harvesting further 0.28% of total annual rainfall the 23% of total cultivable land of Tharparker could also be cultivated to produce low delta Rabi crops enough to meet entire food needs of people and to cope with hunger during frequent droughts periods in the area.

Sukaar Foundation with support from Water Aid in Pakistan, as part of its “Thar Desert Rainwater Harvesting Initiative” has been introducing three tiered inputs in villages of Thar including: (1) to evolve and strengthen grassroots mechanism for managing and maintaining community based rainwater harvesting, (2) design and develop village based rainwater harvesting system, building upon indigenous wisdom integrated with innovative technical and architectural inputs and (3) emphasize on wider advocacy for promotion of rainwater harvesting initiative at districts and provincial level.

This paper reviews basic rainwater harvesting techniques used in villages of Thar and also briefly presents how RWH is being implemented in different villages of Thar using a local wisdom in designing & implementing the systems. The paper also attempts to present the preliminary results of Sukaar’s RWH work which has significant impact on the lives of the villagers through accessibility to water round the year. This has also resulted in saving time and human effort in collecting water and boosting of village economy through improved sanitation situation, increased livestock production, improved vegetation, better groundwater recharge and better human health. The project has also proved to be women-and child friendly by reducing their workload.

The overall project infrastructure development cost amounts to be Pak Rs.3000 per person for providing drinking water throughout the year. This means that by investing Rs. 3 billion, we can secure drinking water and livelihood of the one million population residing in Tharparker.

Starting with Background of Tharparker :

  • Rain dependent population – 1.2 million
  • Poverty Rate – 70% (Double than other districts)
  • Most Food Insecure District (WFP-2000 Survey)
  • Ground Water Needs – 95% of the total population
  • 89% Ground Water is Saline (WHO Reports)
  • 11% of groundwater table continually declining
  • Extensive evaporation: about 60% (cumulative evapo-tranpiration 95 to 98 %)
  • Recharge rate less than 1 per cent
  • Total rainfall in Tharparker – 10 billion M3
  • Domestic water use – 0.25% of rainfall
  • Traditionally used rainwater : 0.06 (25% of domestic water use)
  • Enhancing the RWH capacity by four times can solve the water problem in entire Tharparker.

Rational for RWH in Tharkarker:

  • Increased quality and quantity of ground- and surface water
  • Piped water supply systems – Complex
  • RWH – A simple and adoptable technology.

Village-Based Rainwater Harvesting Initiative: Mr. Nazir mentioned as a model – a) Chalho Pond, b) Chonra Pond, c) Nadi Pond with Geo-Film (HH Level),d) Nadi Pond -1 (School Level), e) Up-Gradation of conventional Ponds. Also Rooftop Water Harvest, Dug well recharge, Jute filters, Bio-Sand Filter etc.

Implementing this technology achievement are as follows: i) daily Water consumption increased by 114%, ii) 61% adult males, and 71% children relieved of fetching water even against increased consumptions, iii) about 72% of strenuous labor saved, iv) Income increased by Rs 3.1 M (39%), v) Expenses segregated by Occupations-on food up by 24%, vi) Diseases of skin, kidney, stomach and female reproductive tract decreased by varying percentages, vi) Drinking water made available that is 20 times cleaner than ordinary collected rain water, vii) In animals: milk & production increased.

Challenges: Regular water quality monitoring by the community people, regularly maintenance of hand pumps is a big deal for the community people because not able to provide information. Involving of local Govt. they will not achieve the level of requirement of the project.

Sustainability & Way forward:

Investing PKR.3,000/person; the total of PKR. 3 billon can solve domestic water problem of Thar. Also lead to kitchen garden, off-season farming to support livelihoods of poor in droughts. Advocacy in the area is formulating. Try to involve large level like other community, Government, NGOs to replicate the model argument initiatives.

Paper 2: Urban RWH in Bangladesh-experiences, potentials and challenges by Ms. Hasin Jahan

Dhaka, with its status of the 19th most populous city is facing an enormous challenge to provide the basic needs to its ever-increasing population of over 13 million. Each year, on the onset of summer, there are severe crises of water, electricity and gas supply. Because of rampant public demonstration, armed troops had to be deployed to protect the water pump stations. The supply-demand gap is so wide that the crisis got manifold as the measures taken were not much effective. The root of crisis lies in unavailability of both surface and groundwater. The surface water from polluted rivers is not only inadequate, but also in some cases beyond treatment. The dependency on groundwater supply has also become enormously high, According to a study conducted by the Institute of Water Modeling, the city’s groundwater level is falling by three meters per year. Due to severe electricity shortage, the option of groundwater extraction is also becoming difficult. The quest for water has forced people to use contaminated sources of water, triggering a massive diarrhea outbreak in every summer, mostly affecting children. On the other hand, during monsoon, the suffering of people increases with a contrasting problem, that is, water logging. Even relatively low intensity of rainfall causes inundation in the low-lying, built-up areas several times a year on a various scales. Usually, the depth of water reaches as much as 40-60 cm, causing a serious threat to health, well being and also huge economical loss. Consequently, the prevalence of various water borne diseases, including diarrhea is also higher during monsoon due to water logging. Thus, the residents of Dhaka city have become captive to the natural and manmade hazards. It has become inevitable to find an alternative and effective solution to reduce the apathy of the residents. Towards that goal, rainwater harvesting system (RWHS) has been identified as a long-term and effective solution to decrease the demand-supply disparity of water in the city. It is estimated that RHSs could supply more than 15% of Dhaka’s thirst with an annual average rainfall of 2,200 mm. The process of rainwater harvesting encompasses catching rainwater using simple techniques such as jars and pots as well as engineered techniques; directing it to an appropriate location; and filtering it if required. The rainwater collected then can be stored for direct use or recharged into the ground water. Water can be stored for four to five months without bacterial contamination, thus possibly reducing the incidence of diarrhea. On the other hand, the recharge of groundwater would raise the water levels in wells and bore wells that are drying up.

Towards the goal, two renowned institutions WaterAid, Bangladesh and Independent University, Bangladesh (IUB) have come forward to set up RHS at the University’s premises to minimize groundwater extraction, the data for which would be collected in the month of April-May. The idea is to provide benefits to its approximately 4,500 students and 410 management and faculty members so that they can share their experience of using an alternative option of water supply.

Ms. Jahan focused on the following urban water supply-demand condition i.e. excessive groundwater abstraction:

  • Dhaka WASA abstracts groundwater using 614 production tubewells which stands around 85% of its total city supply
  • It does not include the extraction of groundwater by more than 2,000 private wells serving highrise buildings, institutions etc.
  • Groundwater Depletion-3 meter per year as a result reducing the natural recharge.

As an experiment introducing a Pilot project of Dhaka WASA & Institute of Water Modelling (IWM). On-Artificial recharge to Dhaka Aquifer. Now significantly artificial recharge has positive impact on groundwater level.

  • Wateraid Bangladesh experience to minimize groundwater extraction set up RWHS project on-BUET(catchment-890sqm), NGO-VERC(catchment-335sqm),Public Works Department’s building, PWD building, IUB building etc.

Potentials of RWH:

It is estimated by IWM that if 60% rainfall from roof top in Dhaka city can be harvested, then about 200 MLD water can be made available. Approximately 15% of the annual demand of Dhaka city can be met from harvested rainwater.

Challenges:

  • Sensitize and aware mass people
  • Develop trained professionals and practitioners
  • Incorporate RWH in the curriculam of technical institutes
  • Link research with implementation
  • Promote good practices and engage private sectors especially the real estate companies.
  • An important milestone has already been achieved through incorporation of RWH in the draft Bangladesh National Building Code, which is under approval process, but enforcement will be even more of a challenge.

Paper 3: Water quality improvement in Coastal aquifers of Khulna-Satkhira regions of Bangladesh through managed aquifer recharge: site testing result by Mr. Kazi Matin Ahmed.

Mr. Matin mentioned on his presentation areas with needs for application of Water Buffer

  • Dhaka City and Barind Tract with declining groundwater levels;
  • Jessore area with arsenic in water and declining water level;
  • Hill Tracts with deep water level; and
  • Coastal Area with high salinity in surface and groundwater.

The applicability of various techniques in the identified zones need to be assessed by pilot studies and if successful has to be adopted as a management option to augment the depleting groundwater resources of Dhaka aquifers and also to avoid adverse environmental impacts. Finally eight methods for twenty four specific sites have been recommended to increase aquifer storage. Rooftop rain water harvesting, wetland preservation, dredging of some rivers is recommended to enhance aquifer recharge and storage. Large Diameter Well Drilling Methods: Rotary Drilling, Percussion Drilling has also been suggested.

Locations of Tested and Constructed Sites:

1. Assassuni DPHE Compound, Satkhira:

  • Four wells: two 22 inches and two 12 inches
  • 45 ft casing, 30 ft screen
  • Rooftop rainwater and pond water as source of infiltration
  • 13 piezomteres for manual monitoring and one with diver.

2. Gangarampur, Botiaghata, Khulna:

  • Four wells at sites to a depth of 60 feet, all 22 inches diameter
  • Casing 30 feet, screen 30 feet
  • Pond water infiltration only
  • Piezometers for manual measurement, one with divers.

3. Laskar, Paikgachcha, Khulna:

  • Six wells to a depth of 70 feet, all 12 inches diameter
  • 20 feet casing, 50 feet screen
  • Infiltration from rooftop rain water only
  • 17 piezometers for manual monitoring, one for diver

4. Munshiganj, Shyamnagar, Satkhira:

  • Four wells to a depth of 80 feet, all 12 inches
  • 30 feet casing, 50 feet screen
  • Infiltration from roof top rainwater
  • 13 piezometers for manual measurements, one for diver

The results of this investigation indicate that Dhaka has high potential for artificial recharge, which can play a critical role in maintaining a sustainable water supply for the city dwellers. Remote sensing data, conventional geological data, and GIS overlay analyses provide a powerful and practical approach to identify potential zones for artificial recharge.