PHYSICOCHEMICAL CHARACTERISTICS OF UNDRAINABLE WATER DAMS UTILIZED FOR FISH REARING IN THE SEMI-ARID NAROMORU AREA, CENTRAL KENYA

Abstract

Naromoru is a semiarid area in Central Kenya, occurring on the leeward side of Mt. Kenya.  Its  water  sources  include  a  few  permanent  rivers  such  as  Nairobi  River, intermittent streams and a large number of undrainable water reservoirs. Most of the undrainable water resources have been stocked with fish but their utilization for  fish  rearing  has  generally  remained  very  low.  The  purpose  of  this  study  was therefore to examine the water quality status of the dams to assess their suitability and  potential  for  fish  production.  pH,  electro-conductivity  and  total  dissoved solutes  (TDS)  were measured  in-situ  from  three  reservoirs  (Gathathini,  Lusoi  and Kianda  dams)  differing  in  their  habitat  characteristics.  Water  samples  were collected  for  determination  of  the  ionic  concentartions  of  the  reservoirs.  Water quality  status  differed markedly  between  sites,  with electric  conductivity  ranging from 350μScm-1at Gathathini dam to over 1350μScm-1at Lusoi dam. pH however showed  only  a  slight  variation  from  8-9.6.  Water  temperature  and  transparency varied  significantly  between  the  sites,  while  cationic  constituents  (Ca2+,  K+,  Mg2+ and Na+), anions (SO42-, HCO32-, and Cl-1), heavy metals (Pb2-and Cu2+) and nutrients (NO3-and PO42-) were all within the recommended WHO levels for fish production. Generally  the  water  quality  status  was  within  the  standards  recommended  for fisheries production.