EVALUATION GROUNDWATER USING …geology.uonbi.ac.ke/sites/default/files/cbps/sps/geology...Title...
Transcript of EVALUATION GROUNDWATER USING …geology.uonbi.ac.ke/sites/default/files/cbps/sps/geology...Title...
THE UNIVERSITY OF NAIROBI
SCHOOL OF PHYSICAL SCIENCES
DEPARTMENT OF GEOLOGY
SGL 413: PROJECT IN GEOLOGY
TOPIC: EVALUATION GROUNDWATER USING
ENVIRONMENTAL ISOTOPES: A CASE STUDY OF
MERTI AQUIFER.
BY:GEORGE IGUNZA MULUSA
REG. NO:I13/2536/05
ADVISOR:
PROF. E.O.ODADA
A dissertation submitted in accordance with the requirement for a partial fullfilment of the
Bachelor of Science degree in Geology.
DUE: 27TH FEBRUARY, 2009
ABSTRACT
The evaluation of ground water quality in Merti aquifer was studied using environmental isotope
data of approximately 130 locations collected during 1974 to 2002. The principal evaluation
methods included hydrogen, oxygen and carbon stable isotope ratio analysis, radiocarbon and
tritium dating. The main conclusions are as follows.
Significant differences are observed in the stable isotope compositions. The combined isotope
data suggest that deep groundwater east of the area was recharged during periods of between
12,000 and 19,000 years ago. At depths -:::200feet, ground waters east of the area range in 14C
ages from 2400 to 12,000 years due to shallow mixing of younger water with older groundwater
ascending under hydraulic head into the discharge area.
Only two groundwater sources were observed to contain tritium at concentrations above the
background level. Both of these sources are from the Long Valley area. The lack of tritium in
other groundwater samples indicates that modem recharge «45 years) is not present in
detectable amounts in many of the wells.
Previous studies have outlined the general distribution and characteristics of groundwater
resources in Eastern and Northeastern Provinces. Between 1969 and 1973 The Kenyan
government drilled boreholes, with assistance from external donors, to study the groundwater
dynamics of the area. This project established the existence of fresh water at Yamicha,,northwest of Habaswein, as well as the presence of fresh water in the central part of the Merti
aquifer along the Ewaso Ng'iro drainage. However, saline groundwater also occurs over broad
areas along the flanks of the fresh water zone of the Merti aquifer. Radiocarbon and tritium
samples analyzed by the US Geological Survey in the 1970s suggest that groundwater in the
Merti aquifer is recharged during major floods that may occur on a time scale of a few hundred
to a few thousand years, however the complex carbonate geochemistry of the aquifer made it
impossible for the USGS study to assign more ages to the recharge events. Evaluation of the
groundwater is essential for the development of civilization and to establish a database for
planning future water resources development strategies.
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