Determining the assimilation capacity of lake Tana: focusing on anthropogenic activities
Student name: Mr Hailu Sheferaw Ayele
Guide: Dr Prateek Sharma
Year of completion: 2012
Host Organisation: College of Agricultural and Environmental Science, Bahir-Dar University
Supervisor (Host Organisation): Dr Belyneh Ayele
Abstract: Surface water pollution becomes a problem, when it exceeds the self purification capacity of water
bodies. Lake Tana which is home town of 2,000, 000 population in its catchment its assimilation
capacity still is not well understood. In this research the assimilation capacity of lake Tana, for the
spring season are estimated by taking in to account the nature of the lake, concentration of WQP in
the inflow stream and in the out late river by using a transfer function.
Concentration of TDS, BOD, PO4
3-
, NO3
-
, Cland
SO4
2-
in the lake, out late and inflow water bodies
were measured in the field using digital WQP measuring instruments and in laboratory using UV
visible spectrometric and photometer and the waste loading in to the lake were calculated using
mass balance equation derived for complete mixed system lake.
The output data from the field measurement, laboratory analysis and the transfer function were
analyzed using Minitab and SPSS statistical package soft-wares.
The result showed that the lake were a complete mixed type lake in which chemically homogenous
and no significant difference were observed in concentration of WQP between the in lake and out
late water bodies.
Finally, the lake had transfer function (β = 0.485, 0.886, 0.523, 0.859, 0.718, 0.751 averagely per
month for TDS, BOD, PO4
3-
, NO3
-
, Cland
SO4
2-
respectively which are fall in the range of good
assimilation capacity (β << 1 ). Hence, Pollutant emission from the environment should be in the
permissible limit of surface water quality standard to maintain the lakes self purification mechanism.
Key words: Lake Tana, Assimilation capacity, mass balance, Water Quality parameters, transfer
function.
