Presentation is loading. Please wait.

Presentation is loading. Please wait.

GROUNDWATER RECHARGE AND FATE OF GROUNDWATER STORAGE OF THE WEYBO RIVER CATCHMENT WELAYITA-HADIYA ZONES SOUTHERN ETHIOPIA.

Similar presentations


Presentation on theme: "GROUNDWATER RECHARGE AND FATE OF GROUNDWATER STORAGE OF THE WEYBO RIVER CATCHMENT WELAYITA-HADIYA ZONES SOUTHERN ETHIOPIA."— Presentation transcript:

1 GROUNDWATER RECHARGE AND FATE OF GROUNDWATER STORAGE OF THE WEYBO RIVER CATCHMENT WELAYITA-HADIYA ZONES SOUTHERN ETHIOPIA

2 BACKGROUND  Most activities come to rely on groundwater resources than on surface water resources mainly due to their sustainability and quality  The Potentialities of Groundwater resource is mainly factored by the Rate of Recharge  Changes in the Geo-Environment of the catchment and the entire Omo-Gibe Basin is manifested by changes in Recharge Rates

3 OBJECTIVES u Estimating the Optimum Groundwater Recharge uShowing the Temporal-Trend of Recharge w.r.t. the Temporal Changes of the Hydro- Meteorological Parameters uAssessing the Fate of Groundwater Storage uTo Show the Major Controlling Parameter of Groundwater Recharge in the Catchment

4 DISTANCE FROM ADDIS ABABA AND ALTERNATIVE ROADS Along Addis Ababa – Butajira – Hosaina Road = 300Km Along Addis Ababa – Shashemene – Welaita Road = 410 Along Addis Ababa – Durame – Areka = 440Km AREAL EXTENT = 574Km 2 PERIMETER = 124Km ’ ’28N ’ ’40E

5 PHYSIOGRAPHY  50% of the area has a slope 2-6%,  25% has 0-2%,  15% has 6-12%,  6% has 12-24% Elevated areas are found in the boundaries of the area Topographic relief ranges from m from the highest peak Damota to the lowest Weybo valley

6 GEOLOGY  The main lithologic units that are outcropped in the study area and near to its adjacent watersheds are the teritiary volcanics  The Nazareth Groups (of Miocene to Pliocene age) and the flood basalts (Eocene to early Miocene age) are the dominant units that widely cover the study area  About 90% of the area is covered by the Nazareth Group, which comprises of a series of rhyolite-trachyt flows, ignimbrites, pumice and ash falls  The Nazareth Group unconformably overlies the early flood basalts

7

8 HYDROGEOLOGY HYDROGEOLOGIC UNITS AND AQUIFER SYSTEMS AQUIFER FORMATION -Weathered and fractured ignimbrite/welded tuff -Sediments associated with weathered pumice -Weathered and fractured rhyolites and Trachytes TYPES OF AQUIFERS IN THE CATCHMENT -Dominantly leaky aquifers

9 HYDROGEOLOGICAL MAP OF THE STUDY AREA

10  Correlation has been made between Geological structures and hydraulic conductivity values  A greater extent of the study area possesses a low permeability zone. HYDRAULIC CHARACTERISTICS

11 GROUND WATER FLOW SYSTEMS AND POTENTIOMETRIC CONTOURS Regional, intermediate and local flow systems

12 RECHARGE AND DISCHARGE ZONES  Zonation based on topography

13  Zonation based on peizometric patterns Flow lines tend to diverge from recharge areas and converge toward discharge zones

14  Zonation Based on Hydro chemical Trends

15 HYDROMETEOROLOGY PRECIPITATION = 1340 mm TEMPRATURE = C RELATIVE HUMIDITY = 63.5% MEAN WIND SPEED = 2.45m/s POTENTIAL EVAPOTRANSPIRATION = mm ACTUAL EVAPOTRANSPIRATION (AET) = 960.3mm

16 STREAM DISCHARGE OF WEYBO RIVER (i)Scaling up the stream flow values Q mouth = (A 2 /A 1 ) Q gauged Q = Q an (P an /P) (ii) The analogue method

17

18 GROUNDWATER RECHARGE (GWR)  CONVENTIONAL WATER BALANCE APPROACH GWR = 88.19mm/annum  STREAM HYDROGRAPHS ANALYSES Mean long-term minimum flow = 62.5mm/year Seasonal recession method = 74.5mm/year  CHLORIDE MASS BALANCE = 123.5mm/year

19 THE OPTIMUM GROUND WATER RECHARGE ESTIMATION BASED ON GROUNDWATER BUDGET ESTIMATED GROUNDWATER OUTFLOW = GW INFLOW ESTIMATED FROM WATER BALANCE AND SEASONAL RECESSION METHOD = 81.5mm THE OPTIMUM GROUND WATER RECHARGE = 81.5

20 TREND OF GROUNDWATER RECHARGE

21 FATE OF GROUNDWATER STORAGE Groundwater storage will be heavily affected and appreciable change in storage will be seen after 30 years now on Equating the linear equation: y = -587x

22 RECHARGE TREND W.R.T. CONTROLLING HYDRO-METEOROLOGICAL PARAMETERS Mean precipitation is slightly decreasing, however, its rate of declination is not comparable

23 mean temperature shows an increasing trend mean wind speed shows an increasing trend

24 potential evapotranspiration is slightly increasing

25 -Groundwater recharge is computed using 4 different Methods and four different values are obtained. The optimum=81.5mm -The decline in groundwater recharge is highly attributed to changes in the environment -Measurable changes in groundwater storage will be seen in a 30 years period of time if environmental changes are keeping on the same rate CONCLUSION -The groundwater recharge estimated from measurements of chloride yields an over estimated result.

26


Download ppt "GROUNDWATER RECHARGE AND FATE OF GROUNDWATER STORAGE OF THE WEYBO RIVER CATCHMENT WELAYITA-HADIYA ZONES SOUTHERN ETHIOPIA."

Similar presentations


Ads by Google