Gebreezgi, Afework Hailu (2010) Aquifer Characterization of the Raya Valley Based on Pumping Test and Geophysical Data Analysis. Masters thesis, Addis Ababa University.
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Abstract
This work has focused on the quantitative characterization of aquifer hydraulic parameters of the raya valley by establishing a relationship between aquifer properties (specific capacity and BH yield data with transmissivity and between aquifer hydraulic parameters and aquifer electrical properties i.e. Transmissivity and transverse resistance aiming to extrapolate measured aquifer hydraulic parameters to an area with no pumping test data using the established relationships between T and Sc, T and BH yield and between T and R. Before establishing relationships between aquifer hydraulic parameters and aquifer hydraulic and electric properties a huge volume of raw data set are analyzed using different softwares. 135 raw pumping test data are analyzed to determine T & K from constant and recovery. 49 wells tapping unconfined aquifers are corrected for decreasing saturated thickness using Jacob correction method and 64 wells whose pumping rate exceeding 36 l/sec are corrected for well loss using step drawdown test data by employing the Hantush- Bierschenk well loss solution method. Three methods are applied to determine a relationship between T and Sc and one method between aquifer hydraulic and electric properties. By using the three approaches of estimating T from Sc i.e. analytical, empirical and geostatistical a regressed relationship between the parameters (T & Sc) for each approach is established with R2 value >0.95 and interpolated map of transmissivity and hydraulic conductivity are created through geostatistical approach by using cokriging and kriging techniques for T from Sc and K from K respectively. The results of analytical and empirical techniques are compared based on their mean error and mean absolute error and it is found that the mean absolute error and mean error for transmissivity estimated using the analytic approach are 0.21 and -0.21 respectively. A mean absolute error of 0.21 means on average, the estimated value of T is within a factor of 1.6 of the measured value. The mean absolute error and mean error for T estimated using the empirical approach are 0.073 and 0.00021 respectively. A mean absolute error of 0.073 indicates that, on average, the estimated value of T is within a factor of 1.18 of the measured value. The established relationship between T and BH yield data also shows BH yield can also be a fair estimator of T in areas with only BH yield data. This has a goodness of fit above 0.8. The T and R of the aquifer are also linearly related with R2>0.95 using an empirical relation and this can be used to extrapolate PT data to an area.
| Item Type: | Thesis (Masters) |
|---|---|
| Subjects: | Q Science > Q Science (General) Q Science > QC Physics Q Science > QE Geology |
| Divisions: | Africana |
| Depositing User: | Selom Ghislain |
| Date Deposited: | 12 Jun 2018 11:57 |
| Last Modified: | 12 Jun 2018 11:57 |
| URI: | http://thesisbank.jhia.ac.ke/id/eprint/4163 |
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