Eastern Produce Malawi - Water resources assessment

Eastern Produce Malawi - Water resources assessment

Aquaquest limited was retained by Eastern produce of Malawi to undertake an assessment of the ground water potential and the surface containment to support irrigation farming.

Eastern Produce Malawi operates several estates in Thyolo area located in Southern Malawi. EP is planning on developing macadamia as a crop, for which there is need for irrigation water. In total there is need to meet approximately 1,500 hectares, consisting of approximately 1,200 hectares of mature trees, 280 hectares immature trees and 40 hectares of new plants; totalling 250,000 trees.

The focus of this project was solely desk-based and depended on accessible information and satellite imagery.

The following approach was taken in order to successfully execute the project;

  • Undertaking of data review identifying existing boreholes in the area and collecting relevant literature and maps
  • Analysing the geological formations and hydrogeology in the area to identify potential for ground water using bulk density models with aggregated climate date
  • Assessing surface water catchments and streams to determine total availability
  • Mapping elevation to determine potential for dams sites

The assessments were done in two parts which are Groundwater assessment and Surface water assessment, and included advice on locations for placing surface dams.

Ground Water Assessments for SeedCo Mpelembe farm

Ground Water Assessments for SeedCo Mpelembe farm

Water is a very important natural resource and vital for life or any development of land. In some parts of the country there is limited or no access to surface water and so the only alternative is ground water. And so for the fact that ground water exists in the subsurface and cannot be seen, studies and assessment are done in order to determine the potential of ground water on a particular land of interest.

Aquaquest was hired by SeedCo Company to assess the ground water potential for a farm located in Kabwe, Central province Zambia. The main objective of the project was to assess the ground water potential of the 2,600 hectares (ha) of which about 195 ha is under pivot irrigation(3 pivots of approximately 65 ha size). The remaining area is covered by natural vegetation and used for cattle rearing.

The main activities included:

  • Site visit to Mpelembe Farm to map the property boundary, geology and existing water supply.
  • Analysing the geological formations and hydrogeology in the area to identify potential for ground water using bulk density models with aggregated climate date.
  • Prepared final report covering all findings and recommendations on water availability in different climate change scenarios.

An initial desk study was carried out in order to identify interesting locations to physically check during the planned site visit. A site visit was carried out by Aquaquest personnel in which mapping of the property boundary, geology, and existing water supply was successfully done.

A total twenty (20) boreholes were identified and geographic coordinates collected.  All boreholes were fitted with 152mm (6-inch) diameter casings.  Measurements were made on all accessible boreholes to measure shallow water levels.

Two surface dams are constructed on the farm and both were dry during the time of the site visit. The dams were both constructed with local soils and they appear to extend 1 m to 1.5 m in height and are approximately 310 m and 510 m in length, respectively.

Two reservoirs are constructed to supply water to the pivots. Each has a pump house containing the pumping equipment. They are located adjacent to the pivots. Both were reported to be operating.

Aquaquest also collected some samples of rocks found on site to help understand the local geology of the area. The samples were later brought back to the office to be analysed and correlated with geological maps.

A review of all the data collected and available data was done in order to develop an understanding of the ground water regime beneath and in the immediate surroundings of the farm. The important aim of the review was to identify features such as fractures (faults, fracture systems, zones of tensional release, etc), topographical lows, preferential flow paths, catchments areas, water divides and geological features such as contacts and intrusions that enhance the potential for ground water.
All data collected in the field was processed and analysed in the office. This data combined the all available data reviewed was then summarised in to a report which included field observations, data analysis, conclusions based on data and recommendations to the client.

Hydrogeological Survey in Meanwood Ndeke, Lusaka

Hydrogeological Survey in Meanwood Ndeke, Lusaka

As the demand for land and accommodation increases in Zambia, and particularly in the Capital city Lusaka, there has been an increase in the number of houses being built and housing developments constructing housing. This has also seen the mushrooming of unplanned settlements and Aquaquest Limited recently undertook a project to carry out Hydrogeological Surveys of two Housing estates namely Meanwood Ndeke and Vorna valley located in Lusaka, Zambia. The two areas currently have no access to council water or sewerage facilities, as a result most of the residents have drilled private boreholes and constructed private sewerage systems such as septic tanks on their properties. The Lusaka Water and Sewerage Company (LWSC) via funding from the Millennium challenge account is now installing a water reticulation system to cover the water supply and sanitation for both Meanwood Ndeke and Vorna valley.

The area has no access to a good source of surface water as such the only viable source of clean water is ground water. Before Aquaquest was retained to carry out the survey, a drilling contractor was hired to drill boreholes and secure enough water to feed the two housing estates. The drilling contractor however did not find enough water to feed both estates.

Aquaquest was retained by the main contractor on the project who was assigned with the task of constructing the water reticulation system of the two estates. In order to achieve this Aquaquest undertook investigations which consisted of the following;

  • Conducting a limited review of available hydrogeological data
  • Conducting a site reconnaissance including preliminary mapping of the geology, and
  • Undertaking focused geophysical surveying

A data review was conducted with the aim of developing a general understanding of the local hydrology and gaining an insight in the local ground water regime. It made use of available information covering: climate, general geology, topography, aerial and satellite imagery, from which maps were generated.

Aquaquest performed a short field reconnaissance prior to initiating the surveying in which existing sources of water(such as boreholes, shallow dug wells, streams, etc.) were identified and assessed characteristics, such as vegetation, soils, accessibility etc.

The geophysical surveying consisted primarily of resistivity profiling with selected follow up vertical electric soundings, to assist in identifying low resistivity zones/ conductors such as:

  • Near vertical zones of fractured or faulted rock, and
  • Areas of substantial thickness of weathered overburden

Surveys were conducted using an ABEM SAS 300 Terrameter with a spread configuration giving a depth of investigation of around 75m – 90m.

The resistivity profiling assists in identifying lateral variations at a constant depth. Sites of ground water potential are identified based on profile shape and resistance readings. The profiling set up uses the schlumberger configuration and consists of a total electrode spread (AB) of 180 m with readings taken every 10 m.

Aquaquest carried out two weeks of field Geophysical surveys to help locate possible drilling locations for ground water abstraction.

It was also a tricky project to work on as most of the area has been developed and is also still under construction, with power lines and boundary walls interfering with the readings. The ideal situation is that before construction of houses starts on any housing estate, a sustainable water source should be secured and a proper water reticulation system installed. Nonetheless Aquaquest successfully finished the work and reported recommendations to the client.

Development of a private irrigation system for a client in Lusaka

Development of a private irrigation system for a client in Lusaka

Aquaquest was hired by a client under take the development of a private irrigation scheme for his property located off leopards hill road in Lusaka. The watering was meant to cover a vegetable garden, a lawn area and macadamia orchard. The Main objectives of the project were:

  • Supervision of all drilling activities and construction of a borehole
  • Test pumping of the borehole
  • Sizing and recommendations of the borehole pump
  • Supervision of the installation of the reservoir and irrigation pump
  • Design of irrigation system

The client hired a drilling contractor to undertake all drilling and construction activities. Aquaquest was on site to provide independent observation and technical input of all drilling and construction activities. The drilling overall resulted in the drilling of three exploratory holes and construction of one production well.

The next step was to carry out test pumping of the newly constructed production well in order to establish a sustainable rate of pumping.  The water from the borehole was meant to maintain a recently constructed reservoir, to provide water for the vegetable garden, lawn and macadamia orchard.

Results from the test pumping were used to size the pump to be used for filling the reservoir and set a sustainable pumping rate. Subsequently a pump was procured and installed in the borehole to supply water to the reservoir.

Aquaquest ltd then designed the irrigation system; which included preliminary and final design, sizing, installation and testing of the pump used to provide water from the reservoir to the irrigation network. Construction of the watering system was done by a private contractor hired by the client with technical input from Aquaquest.

The irrigation system was successfully installed by the contractor and Aquaquest was on site to test the yields from the taps and outlets to see if it was sufficient for irrigation.