Hydraulic ram pumps and Sling Pumps

D WATER RESOURCES AND USE: FELLINGAoped in the same manner. The construction is brieflydescribed in the 8 different steps that follow below.Step 1Site clearing is done to get a clear view of the actual layoutof the spring and at the same time it will create space fortemporary storage of construction materials. All bushesand trees including the roots are removed in the vicinityof the spring. Large trees are normally left untouched asit is felt that removing them will do more bad than good.At some places site clearance and excavation of the springis a very sensitive matter. People in Bhutan believe thatlocal deities reside near the spring and protect the continuityand cleanliness of the water. Any human activitynear the spring may make the deities angry and will resultin drying up or shifting of the outlet. These feelingsshould never be taken lightly and discussions with thecommunity are needed to resolve these problems. Monksare often consulted because of their influence in thecommunity and their ability to perform religious ceremoniesfor the deities.Step 2Before the excavation starts it is important to mark thepresent level of the spring water table. The level of overflowshould not be above this mark because else there willbe a chance that the spring will shift to a nearby outletwith a lower hydraulic resistance. Excavation is donewhile the water is freely flowing out of the spring. Duringexcavation no dams are built because an increase in theresistance (due to an increased outflow level) might causethe spring to disappear. For the same reason it is equallyimportant not to disturb the impermeable layer. Excavationshould continue up to the point where the waterappears from the permeable layer. Depending on thelayout of the spring, side branches in the excavation haveto be made. This can result in a straight, Tee or Y shapedtrench system. During excavation the stability of theslopes should always be guaranteed and excavated materialsshould be stored sufficiently away to avoid slopeoverloading resulting in collapsing of trenches. Duringexcavation guidance from a experienced technician isessential because it is difficult to predict the final layoutbeforehand.Table 1. Pipe sizes open fountain systemExpected maximumyield< 1.5 l/s1.5 - 3.0 l/s3.0 - 5.0 l/sOutlet pipeGI medium1”1”1”Overflow pipeHDP 6 kgf/cm 21 x 63 mm2 x 63 mm3 x 63 mmthe outlet-pipe the overflow pipes are placed 10-20cmabove the outlet but not higher than the level mark of theoriginal spring water-table.The materials for the spring development of OpenFountain Systems are standardised for reasons of simplicity.The outlet pipe and overflow pipe have fixed diametersregardless of the natural yield and distribution flow.For springs with a high yield the number of outlet pipesis doubled or even tripled (see Table 1). The outlet pipe isan approximately 2 meter long, slotted HDP strainer, of32mm diameter. The slots with a width of 3-4mm aremade with a hacksaw and are facing upward whenplaced in the trench. Burrs must be removed to reduceinflow resistance. The HDP strainer is shrunk over the 1”GI pipe. Also the overflow pipe is slotted because the pipeend is easily blocked. Both outlet and overflow pipeshould maintain a slope of 1-2 per cent down in theoutward direction.When the yield is measured during the dry season anincrease in yield in the rainy season can be expected witha factor 3 to 6 depending on the topography, geology andland use of the catchment area. Since it is difficult topredict the maximum yield, it is better to design safe andprovide sufficient capacity for the overflow.Figure 1. Schematic diagram of open fountain systemStep 3Once trenching is done a final decision is made on thelayout of the spring protection and shape of strainer pipe.HDP strainers will be in all individual trenches when thetrench system is made in a Y or Tee shape. The outlet pipeand strainer(s) are placed in the trenches approximately2-3cm above the floor. A temporary clay wall is built tocreate a dry working environment for the construction ofthe final wall or barrage. This wall is made in stonemasonry with a strong plaster coat (Cement:Sand ratio1:2) on the inside. The outlet pipe will temporarily functionas drain during the construction. After the placing of181