TO ASSESS THE IMPACT OF LANDUSE CHANGE ON NUTRIENTS FLOW AND TO ESTABLISH THE LEVEL OF KEY POLLUTANTS OF NYANGORES RIVER

Abstract

This  study  was  carried  out  with  the  aim  of  assessing  the  effect  of  riparian  land  use/  land  cover  change  on  the hydrology  and  water  quality  of  the  upper  Mara  River  catchment  specifically  Nyangores  River.  The  study incorporated  remote  sensing  and  GIS  tools  to prepare  and  analyze  the  data.  It  involved  sampling  of  sediments
deposits and water flows at various points of the river to quantify water quality parameters such as N, P, Ca and Fe. These parameters were tested in the laboratory. Land cover change was  analysed  from dry season LandSat MSS, TM and ETM images of 1976, 1980, 1985, 1990, 1995, 2003, 2006, 2010, and 2014 respectively. Digital image analysis for the riparian zone showed that between 1976 and 2003, crop  land increased by about 100%, other vegetation and forests have reduced by 32% and 34%
respectively  with  the  river  line  decreasing  by  50%.  Comparatively  high  percentages  of  N,  P,  Ca  and  Fe  i.e. 0.07meq/100g  soil,  0.66meq/100g  soil,  12meq/100g  soil  and  17mg/kg  respectively  were  detected  from  soils collected  along  the  cattle  tracks  and  in  the  water  directly  below  the  animal  tracks.  Grass  strips  along  the  rivers
were found to filter sediment and nutrients and soil from the urban set up and tested high for Fe=46 mg/kg, N= 0.03meq/100g soil K=0.21meq/100g soil caused by channelized flow. Soil composition of 89% sand, 3.4% clay and 7.5% silt which is sandy soil forms the downstream banks of river Nyangores and this is the main cause of the river banks erosion and  subsequent sedimentation. Channelization should be controlled and a lot more of grass should be planted along the riparian zone also deep rooted trees should be planted at the downstream of river Nyangores to control river bank Erosion.

Key words: Riparian zone, landuse/landcover, water quality, hydrology