I. INTRODUCTION

1. Ground Water Hand Pumps in Viet Nam

Since the 1980s several organizations (e.g. UNICEF) are running water and hygiene promotion campaigns in Viet Nam. Part of those campaigns is the construction of ground water wells and the installation of hand pumps. For instance, alone in Can Tho Province in the Mekong Delta over 50,000 wells were drilled since 1989. Those wells have diameters between 40 and 45 mm, are approx. 100 m deep and are often equipped with suction-hand-pumps. The most widespread hand pump type is the model “VN6”, a lighter version of the UNICEF No. 6 pump which was originally designed for the drinking water supply in Bangladesh (see Figure 1). The UNICEF No. 6 is characterized by a stable construction and a weight of approx. 33 kg. In Bangladesh usually one pump serves more than 100 people. In Viet Nam, however, the user groups are much smaller. Normally, one pump serves a maximum of 10 people. Under this condition the Bangladesh No. 6 was too heavy and consequently too expensive for the market [4]. For that reason UNICEF introduced the VN6 to Viet Nam. The VN6 weights 22 kg and costs approx. 300.000 VND. The Vietnamese market demands cheaper pumps. Since 1995 counterfeits of the VN6 are pushing into the market. They can be identified by a weight below 20 kg and a fake UNICEF label. The costs for a copied VN6 hand pump is between 80.000 and 100.000 VND.

2. Goal of the Quality Tests

The goal of the tests is the comparison of the well quality including the installed hand pumps. Here, the focus is on the differences between wells with original hand pumps and wells with copied hand pumps. The results are illustrated in efficiency curves. In this first approach the efficiency curves include well characteristics, aquifer characteristics and hand pump characteristics.

3. Study Site

The quality tests were carried out at the village An Binh in the Hậu Giang Province in the centre of the Mekong Delta. Here, ground water wells are very popular. The first wells were drilled in 1995. According to Do Tien Hung [3] there are five major aquifers, whereas mainly the second aquifer is used for ground water exploitation. It’s a confined aquifer (fine to coarse sand), covered by a clay layer with a thickness of 60 m. At both sites, the ground water level is approx. 4 m below surface. Slug and Bail Tests which were performed in An Binh

show a range for the hydraulic conductivities of this aquifer between 1,9 x 10^-4 and 4,1 x 10^-4 m/s [2].

II. METHOD

1. Experiment Set-Up and Procedure

The experimental set-up are illustrated in Figure 2. Firstly, various geometrical data as well as the weight of the pump were documented. Also, ground water level, depth and diameter of the borehole were measured. A water meter was installed for the measurement of the pumping rate. Additionally, a spring scale was attached to the handle of the hand pump.

For the actual procedure of the experiment, ground water was pumped by a test person for about two minutes. The precise duration, amount of the pumping strokes and the volume of the discharged ground water were measured. The power which was necessary for a pumping stroke was recorded by the spring scale.

This procedure was carried out three times. Each time it was pumped with a different intensity to identify a dependency between discharge rate and the brought up power. Additional to the tests, pump owners were asked about maintenance habits and the technical condition of the pump was rated visually.

2. Evaluation

Besides the above listed parameters, following figures need to be calculated for the appraisal of the hand pumps:

- discharge rate (Q)

- brought up power (P)

- efficiency factor (η)

Those figures are determined with the following equations.

Discharge Rate Q

The discharge rate Q is defined as the ratio between the measured discharge volume V and the duration of the experiment t:

Power P

To determine the power P firstly the traction T at the plunger needs to be calculated:

The work W which was brought up during the entire experiment is calculated by multiplying the traction T by the length of the plunger h and the number of the piston strokes n:

Finally, the brought up power P can be calculated by dividing the work W by the duration t of the experiment. Additionally, the brought up power P is referred to the entire pumping height.

Efficiency Factor η

The efficiency factor η is defined as the ratio between the discharge rate Q and the power P. To get a non-dimensional figure the term needs to be multiplied by the density of water ρ and the acceleration of gravity g:

III. RESULTS AND DISCUSSION

A total of 55 wells were found in An Binh. Most of the existing wells were equipped with electric suction pumps. Only 19 of the wells had functioning hand pumps. Three different types of hand pumps were identified. Beside the original VN6 pumps, hand pumps with 15 kg and 11 kg were available. Between 1995 and 1998 solely original VN6 pumps and the 15 kg pumps were installed, whereas especially in 1997 and 1998 the 15 kg pumps were predomi nant. Since 2001 three out of six wells were equipped with the 11 kg hand pumps (see Table 1).

In the figures 3 to 5, efficiency curves of the wells are illustrated. The two wells with the original VN6 hand pumps which were installed between 2001 and 2002 show the highest efficiency. The efficiency factors of the wells with the older original VN6 hand pumps are between 0,6 and 0,8. Wells with the 15 kg pumps show an efficiency between 0,85 and 0,25, whereas the hand pumps of the wells with an efficiency η>0,5 were in a good technical condition. According to the proprietors of those pumps, the maintenance was carried out frequently. Against that, hand pumps of the wells with a low factor (η<0,5) were rarely maintained. The technical condition of those hand pumps was very poor. The efficiency curves of wells with the 11 kg pumps show factors between 0,8 and 0,5. Nevertheless, it can be said that the wells with the 11 kg pumps need more power to reach the same discharge rate as the 15 kg pump and the original VN6.

Table 1. Number of installed pumps

Year of installation	Orig. VN6	15 kg pump	11 kg pump
1995-1996	2	2	-
1997-1998	1	8	-
1999-2000	-	-	-
2001-2002	2	1	2
2003-2004	-	-	1

IV. CONCLUSIONS AND OUTLOOK

Here, wells with the original UNICEF VN6 pumps are - even after several years of intense use - more efficient than most of the younger wells with copied VN6 hand pumps. Only the wells with very carefully maintained 15 kg pumps show a similar efficiency than the wells with the original VN6 pumps. The quality of the new wells with a new 11 kg hand pump is much lower than the quality of wells with the original hand pumps and the old 15 kg copies. Even wells with 11 kg pumps which were only three years old could not reach the efficiency of wells with the eight-year-old original or 15 kg hand pumps.

Overall, with this approach it is possible to quantify the quality differences between ground water wells including the various types of hand pumps. In a next step the influences of the various factors should be quantified. Those factors are the characteristics of the well, the aquifer and the specific characteristics of the hand pumps. Therefore, tests concerning the technical conditions of the borehole, filter screens, well casings, friction of the well-pipes, productiveness and the hydraulic conductivity of the aquifer should be performed. At the same time, tests of the hand pumps - as described above - could be performed under defined conditions. With this approach a general statement about all the components and the their influences could be made and a complete comparison of the wells even at different sites could be possible.

Contact

Environmental Engineering and Ecology
Ruhr-University Bochum
Prof. Dr. Harro Stolpe
Faculty of Civil Engineering
Tel.: +49(0)234 32 27995
Fax.: +49(0)234 32 14701
www.rub.de/ecology
thomas.nuber@rub.de

Acknowledgements

The authors would like to thank the Federal Ministry of Education and Research of Germany (BMBF Germany) for the financial support (Project ID 02WD0414).

REFERENCES

1. Baumann E. 2000. Series of Manuals on Drinking Water Supply. Water Lifting, Vol.7, Skat-Foundation, St. Gallen,Switzerland.

2. Benstöm F., Nuber, T., Stolpe H., 2005. Determination of Hydraulic Conductivity with Slug And Bail Tests in Small Diameter Wells in the South of Viet Nam. In this journal !!!

3. Do Tien Hung, Nguyen Hong Bang, Pham Van Giang, 2000. Availability and quality of ground water resources. Department of Geology and Minerals, Division of Hydrogeology and Engineering for South Viet Nam (DHES), Ho Chi Minh City.

4. Ikin D. & Baumann E., 2002. Appraisal and Impact Assessment of IDE Viet Nam Hand Pump Program. Skat-Foundation, St. Gallen, Switzerland.