Max Karen Hydrogeologist Zambia/Malawi/Botswana

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Allen Osborne
6 years ago
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1 Max Karen Hydrogeologist Zambia/Malawi/Botswana

2 Has a cost effective approach been affective? What is the real cost of a borehole? False economies? Reasons for failure and what we can do about it?

3 Background Massive effort in the rural water supply sector to supply as many people as possible Emphasis has been on numbers to create coverage figures that satisfy donors X million US$ supplies X 1,000 s of people e.g. 1 handpump supplies 250 people But is this a real cost?

4 But are low cost boreholes really cost effective? Most project do not monitor long term performance Usually the project has a fixed lifespan Pressure to supply as many people as possible over a 3 4 year period

5 Has the effort to reduce cost been counterproductive? Anna Karenina Principle It is possible to fail in many different ways This includes the long term as a principle indicator or success

6 Why are boreholes failing? 1. Depth Dry season drilling 2. Wet Borehole Contracts geophysics lowest bid 3. Supervision 4. Gravel Pack 7. Cost Effective? 5. Construction Materials 6. Ownership

7 Case Study 1 Western Zambia Production boreholes drilled in complex unconsolidated sediments Emergency water supply project Many borehole Failures Reports Reconnaissance

8 Subsidence next to Production Boreholes A B C

9 Cracking and damage due to Subsidence A B C

10 Interlinke d

11 A B C

14 Worst Case Scenario: Borehole with small casing and thin gravel pack Best Case Scenario: Borehole with big casing and thick gravel pack high pump yield with sand flow steep cone of depression low pump yield smooth cone of depression rapid, turbulent water influx slow, laminar water influx

15 Laminar to turbulent flow

16 Lack of pumping test information Installation depth Pumps burning Pump size limited power supply pressure to supply Hydraulic calculations

17 Pumping test were essential to establish safe yield All the old boreholes were encrusted but could were rehabilitated as very little cost Most of new boreholes had failed Over 50% of the problem was wrong pumps and lack of electromechanical capacity

18 The old borehole which are close to 30 years old all were rehabilitated and are working perfectly So even if the original borehole were twice as expensive they have lasted 30 years and could very possibly last another 30 years So massive saving on emergency drilling Massive saving on pipe and infrastructure

19 Case Study 2 North West Zambia Major problem in Kalahari sediments with siltation and failure of RWS handpumps Project from 2004 where borehole cost twice the average cost at the time However to date all are still working Massive problem with Iron in the area So are they twice as expensive?

20 Main Difference between expensive project boreholes and cheaper cost effective boreholes All sited using resistivity All boreholes drilled at mm All installed with stainless steel pump components All drilling and construction supervised with local staff trained in house Functionality still monitored by KfW

21 97% of sites working Situation today

22 If a borehole cost twice as much but last for double the time the cost is the same, if they last four time longer they are effectively half the real cost The are other cost saving as the reason for success is based on a number of factors However there is one further factor that is often overlooked

23 Corrosion is a major issue in RWS and ph used to prevent premature failure Effect project and sustainability on many social and technical levels The main point is that installation of GI pipes in aggressive waters reduces life span to as little as a few months What decision makes hear.

24 ph blah blah blah corrosion blah blah blah Sustainability mapping blah blah blah blah SAVING MONEY Engage attention first then outline the technical reasons Installing corrosion resistant pump components saves money Mapping area with aggressive waters saves money

25 Lusaka Aquifer

26 Communication to decision makers Many technical reasons but the key factor is initial cost savings are not necessarily cost effective.

WATER WELL SCREENS. Sébastien BART Bruno BENAGLIA. Padova 15 Febbraio 2010

WATER WELL SCREENS. Sébastien BART Bruno BENAGLIA. Padova 15 Febbraio 2010 WATER WELL SCREENS Sébastien BART Bruno BENAGLIA Padova 15 Febbraio 2010 DEFINE SCREENS Objectives Yield consistent with aquifer capabilities Longer well life High well efficiency with minimum drawdown