MODELING OF GROUNDWATER FLOW AND  ITS  SUSTAINABLE UTILIZATIONS FOR HANTEBET WATER  SHED, TEKEZE BASIN, TIGRAY  (SEHARTY SAMRE WOREDA)
Creators: name: AREGAWI GEBREKIDAN
Publisher: name: National Academic Digital Repository of Ethiopia
Year: 2007

description: Groundwater  is  of  major  importance  to  civilization,  because  it  is  the  largest 
reserve  of  drinkable  water  in  regions  where  humans  can  live,  so  it  is  very 
important  to  calculate  the  quantity  and  quality  of  this  resource  for  better 
protection and management. 
The  project was  carried  out  in  Hantebet  basin,  northern  Ethiopia,  southwest  of 
Adeka  ala  village  at  about  60Km  from  Mekele  town.  The  catchment  is  a  closed 
basin covering an aerial extent of around  24.4 Km2. 
The main purpose of this project work  is to make a quantitative estimation and 
sustainable use of groundwater resource  for domestic,  live  stock and  agricultural 
supply. To  achieve this objective careful  understanding of hydrology, 
hydrogeology and dynamics of groundwater flow  in and  around  the study area 
was mandatory. 
The  geology  of  the  area was  mapped  at  a  scale  of  1 :50,000  and  it  constitutes 
shale,  limestone, siltstone and dolerite geological units. 
In the  hydro  geological  investigation around  108 hand-dug wells were  inventoried 
and  their geologic  and  hydro  geologic  log  was  plotted  in  vertical  section.  Based 
on  these  loges  the  whole  shallow  wells  are  grouped  in  to  nine  major  aquifer 
natures,  and  the  pumping test  data  analysis was  conducted manually on  about 6- 
wells.  The  transmitivity  and  hydraulic  conductivity  of  the  formation  was 
determined  using  Theis-  Recovery  methods.  Accordingly  the  transmitivity  and 
hydraulic  conductivity  potential  of many  of the  aquifer was  obtained  in  the  range 
of  22.62  -  44.81  m2
/day  and  8.38-26.39  m/day  respectively.  Aerial  rainfall 
recharge was  estimated  using  a step-by-step  procedure  of soil moisture  balance 
in the unconfined zone and obtained 297.33mm/year. 
High abstraction  rates  from  Hantebet  aquifer during  the  previous years  lead  to  a calibrated  for  steady  state  condition  by  matching  simulated  and  observed 
hydraulic  head  data  for  the ·period  2006-2007.  The  root  mean  square  error  for 
simulated  hydraulic  heads  for  all  wells  was  36.58  meter.  Simulated  hydraulic 
heads were within ±15 meter of observed values for all observation wells. 
The  results  of  the  calibrated  model  showed  that  the  horizontal  hydraulic 
conductivity  and  transmitivity  of  the  whole  aquifer  was  32m/d  and  45m2
/day 
respectively. 
Using  the  calibrated  model,  water  budget  of  the  whole  model  domain  was 
calculated  with  a  percent  discrepancy  of  0.02.  It  includes  the  following  inflow 
components  to  the  ground water flow  system:  (1)  recharge  from  Constant  Head 
Boundary,  with  a  value  of  21,  109.490M3 
(2)  Groundwater  recharge  from 
precipitation, which  is 392.175M3
/day.Total  inflows were  21,501.66M3
/day 
The  simulated  groundwater  outflow  from  the  system  includes  Groundwater 
outflow by well  pumpage with a value equal to  21,506.12m3
/day. 
The  groundwater  flow  contour map  and  flow  nets  lines  showed  that  there  is  a 
concentration  flow  towards  southeast  and  this  is  an  area  of  discharge  to  the 
surface streams 
Results  on  the  physical  and  chemical  water  quality  assessment  of  the  area 
indicate that most of the water sample  is magnesium chloride type.  Based  on the 
U.S.  Environmental  protection  agency  (1975)  and WHO,  the  groundwater  in  the 
study area  is suitable for  irrigation and  domestic purposes