ASSESING THE FEASIBILITY OF TURNING ABANDONED QUARRIES IN THE TALA-KANGUNDO-MITABONI AREA INTO FISH PONDS

BY

I13/3142/2008GITHIOMI ALICE MURINGE

OUTLINE

Introduction Objectives Study area Geology Pond construction process Discussion Conclusion Recommendations

INTRODUCTION The Tala-Kangundo area is located in

Machakos district, central Kenya about 50 km ENE of Nairobi

This area is well endowed with volcanic tuffs, laterite among others, which are mined for especially the building industry

However, after these deposits are depleted, the quarries are usually left open and unattended to.

Open pits become health hazards. Lands are degraded and rendered

unproductive after quarrying

Intro (cont’d)

INTRO (cont’d)

Aquaculture, can be one ways of solving these problems.

OBJECTIVES To create awareness on the innovative use of

open pits as commercial, recreational and ornamental fish farms.

To asses the feasibility of turning quarries and open pits in the area into fish ponds.

To provide information that aids in ensuring that degraded land is properly rehabilitated and utilized through transformation into fish ponds.

To make a positive contribution towards the empowerment of the communities living in this area both economically and socially.

GEOLOGY Study area- It is enclosed between latitudes 1o 10’S and 1o

22’ S and longitudes 37o 10’E and 37o 22’E with an approximate area of 600 km2

Lithologycomprised of a number of rock units, tuff being one of them

HydrogeologySurface water manifested as streams and rivers, most seasonalGround water also present

SoilsGoverned by underlying rock which determines bulk mineral

compositionClays underlain by biotite granitoid and augen gneisses-

weathering of micas and feldspars into clay minerals

Geo

logy

Quarries and pits

Soils

POND CONSTRUCTION PROCESSThe pond construction process includes;Site selectionPlanning and designConstruction Establishment of vegetative coverPond Maintenance

Site selection

What to consider;Structural geologyWater sources

Structural geology In order to have a functional fish pond, its

wall and floor surfaces should be impermeable.

However, the tuff quarries are highly jointed, laterite also permeable.

This situation is usually dealt with by sealing off the joints and cracks using clay packs or plastic liners.

Since clay is readily found in the area, it can be prepared to the desired form and used to seal off these openings

Structural Geology (cont’d)

Water Sources The primary water source should be able

to regularly supply the ponds with an adequate amount of clean water.

Both surface water and ground water are found in this area.

Surface waters may however not be enough to adequately supply the ponds with adequate amounts regularly.

Ground water will therefore make for primary supply of water

Water SourcesStreams are dominant sources of surface water, but dry up during the dry season.

stream

Planning and Design

Pond design and layout is specific to the type of pond to be constructed.

Excavated ponds are best suited for these areas.

Planning and Design (cont’d)

Planning and Design (cont’d)

General considerations when designing a pond are Pond shapePond size Water control structures.

Pond shape The shape of the ponds is usually in such

a way that the pond blends with the natural topography and landscape among other factors.

In this case, the shape of the ponds is, to a large extent, predetermined by the shape taken by the quarries and pits.

Small adjustments can nevertheless be made where necessary, and with the advisement of the engineers.

Pond size Surface area and volume of the ponds need

to be established for the proper planning, layout and construction of the pond.

Pond capacity will determine the volume of water pumped and drained out of the ponds.

Detailed surveys of these pond sites are required for the proper computation of the various parameters needed to accurately characterize the pond size.

Water Control Structures

Pond drainage should preferably be largely controlled by gravity.

Caution needs to be taken so as not to flood surrounding areas.

Specific and practical drainage channel designs need to be developed.

Construction Before the actual construction process is

carried out, permits from concerned institutions should be acquired.

Environmental impact assessment surveys need to be carried out.

Construction costs need to be established before the construction begins.

Construction equipment should be adequate and suitable for the area.

General site survey and preparation needs to be done

Establishment of Vegetative Cover Soils found in this area are capable of

supporting vegetation

Establishment of vegetative cover (cont’d) Importance of vegetative cover;Enhances aesthetic valueCurbs erosion and siltation of pondMaximizes productivity of land

Pond Maintenance The pond should be regularly examined

to determine any leaking parts and ensure that they are sealed.

Drainage and desiltation of the pond should be done on a regular basis to ensure suitable and optimum conditions for fish farming.

Desiltation and maintenance of drainage channels and other water control structures should be done.

DISCUSSION Mining of tuff and laterite is a major

economic activity that is carried out in the Tala-Kangundo area.

However, this mining is carried out haphazardly without proper planning.

Open pits pose a great danger to the health, economic and social well-being of the inhabitants of this area.

Aquaculture is one of the ways to effectively restore the land to its productivity.

DISCUSSION (cont’d)

Benefits Maximum land use Creates job opportunities Creates microclimate- benefits agriculture

CONCLUSION The tuff quarries and laterite pits in the

Tala-Kangundo area can effectively be turned into fish ponds.

Site surveys and planning need to however be done to determine the most efficient ways to do this.

The health, economic and social well-being of the inhabitants of this area will be improved through the successful practice of aquaculture.

RECOMMENDATIONS Special interest needs to be taken in this area to

ensure the reclamation of the degraded land is done and the possible actualization of putting up fish ponds.

Objective and more detailed geological and geotechnical surveys need to be done in the area to determine the geology of the area, the hydrology and suitable borehole sites in the area and the specific geotechnical characteristics of the tuffs and laterite.

The information obtained from these surveys should be used in the efficient planning, construction and maintenance of fish ponds.

THANK YOU FOR YOUR ATTENTION