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.