Water for the forgotten people -Botswana's revolutionary well-jettingtechnologyby Jonathan Andrews

Digging the well posed no problem for the smallcommunity; attempting to fit a handpump causedthe professionals nothing but frustration. But,armed only with basic equipment, true grit, and alot of ingenuity, the men of the Okavango WaterDepartment made, literally, a technologicalbreakthrough.

BOTSWANA - LAND OF the fabledKalahari desert, where water is a scarceand precious natural resource. Wheregroundwater is sometimes so salinethat its only practical use is for saltproduction. Where water may only befound buried two or three hundredmetres below vast beds of powder-fineKalahari sand.

But not always. Tucked away in aremote corner of this dry republic is theNorth- West District and another extra-ordinary feature of Botswana - the'Jewel of the Kalahari' - the Oka-vango Delta.

With each rainy season in Angola,

the Okavango River swells nearlyseven times from its base flow of 100m3 per second.l Sweet water flows outand over and down into the sands sup-porting abundant wildlife in a won-drous inland delta ecosystem. Withwater and wildlife and vegetation comethe people and with these people ourstory begins.

Tribal landsIt is not easy to count the number oftribal groups in the north west. Herelive the baHeroro from Namibia, thebaHambukushu from Angola, and the

baTwana, baSupia and baKhalagadifrom other regions of the republic.Then there are the ba Yei - the riverpeople - and the baSarwa, the San -the bushmen who call themselvessimply 'the People'. There arecertainly more.

Many of these people live in the 40recognized villages and towns of theNorth West, villages with boreholesand diesel engines pumping water toelevated tanks for gravity-fed tap-standsupply. But this is not a .story aboutthem; this is a tale about a struggle forwater where there is no money for aborehole. A struggle by one districtcouncil-based water department to findwater and keep it flowing for the thou-sands of people settled in small, scat-tered communities where fully reticu-lated supplies are economically impos-sible. This is a tale of the discovery ofa technology that suits the people, theenvironment, and the budget. In theNorth West this technology, howeversimple, means water for the forgottenpeople.

Botswana s Okavango Delta: close to the sand dunes, this inland delta ecosystem is home to a wealth offiora andfauna.

28 WATERLINES VOL. 14 NO.4 APRIL 1996

Principles of jettingWater is pumped down the centre of the drill-rods.emerging as a jet. It then returns up the borehold or drill-pipe bringing cuttings and debris with it. The washing andcutting of the formation is helped by rotation, and by theup-and-down motion of the drillstring. A foot-poweredtreadle pump or a small in~ernal-combustion pump areequally suitable.

Advantages of jetting• The equipment is simple to use• Possible above and below the water-table.

AtfOWS indicatedirectionoffk)w

Cuttingl~

Disadvantages of jetting• Water is required for pumping• Suitable for unconsolidated rocks (eg sand, silt. clay) only• Boulders can prevent further drilling

triumphant, prepared to install thehandpump the following day.

Spurred on by the success of this firstproject, the team continued to experi-ment with new ideas and install similarwell-points in other settlements. Vari-ous problems came to light and proce-dures were adapted to cater for them -the need to maintain the verticality ofthe pipes was addressed by introducinga simple wooden frame whilst jetting.

Innovationin action

experiments led to the development ofa simple jetting head that would directhigh-pressure water to the cutting face.The first of a series of large diameter(l60mm) well-points was manufac-tured at the Gumare water workshop; aSOOO-litre plastic tank and a 80mmpetrol-powered water pump were pur-chased, and the team prepared for theirfirst well improvement by jetting.

In-field proce-dures were thenformulated andtasks delegatedto individuals.The team ranthrough a mockexercise toensure thateveryone knewtheir job beforesetting off forthe communityof Etsha 8, andthe initial field-trial. They com-menced settingup at 1pm and,after workingthrough a fewtechnicalhitches, the firstjetted well-pointwas installedand the equip-ment dismantledby 5.30pm. Asump for thehandpumpexisted now, 5metres belowthe water-table.The team left A completed well-point, showing jetting head and wrappedthe site quite geotextile screen with protective netting sock.

Riddle of the sandsIn many of the small Delta settlements,hand-dug wells are a common sight.Water can often be found 8 to 15mbelow ground. Traditional well con-struction is straightforward and, for thelast ten years, simple improvements,involving the fitting of concrete cas-ings, have been made. The fineness ofthe local sand, however, has blockedprogress in both protecting wells com-pletely, and fitting handpumps. Prob-lems began when crews attempted todeepen well sumps so that hand pumpelements could be fitted. When theyneared the static water-level, the waterflow displaced the sand upwards, and aconventional shovel and bucket well-deepening job soon became a wasteful,not to mention dangerous, exercise.Sand flowed down behind the concretecasing from the surface where hugecraters suddenly appeared. Concretelinings creaked and cracked, andwelldiggers emerged from the groundpale, shaking, and in search of an alter-native occupation.

Nearing their limit of frustration,hand-dug well team members and Oka-vango Water Department2 managers setout to find a solution. They reasonedthat, if the problem lay in the fact thatthe material they were burrowingthrough was weak, then it really shouldbe making the job easier. This sandwas so weak that even the gentle jet ofa garden hose quickly gouged downinto it. Perhaps a step back was neededto capitalize on the virtues of this prob-lematic, omnipresent sand.

After many months of networkingwith water-equipment suppliers,drilling contractors, ex-water-depart-ment workers, and anyone willing tolend an idea, the garden-hose conceptgrew to project proportions. PVC pipeswere slotted by hacksaws, geotextilesock screens were adapted to fit, and

WATERLINES VOL. 14 NO.4 APRIL 1996 29