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Observing Changes in Riparian Buffer Strip Soil Properties Related to Land Use Activities in the River Njoro Watershed, Kenya

13-10-10

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Enanga, Eric & Maina Gichaba, William Shivoga, Irena F Creed

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Water Air and Soil Pollution · June 2011

ResearchGate - Springer Science+Business Media B.V.

ecology environment water quality law and regulations

Riparian buffer strip guidelines are under scrutiny in the River Njoro Watershed in Kenya. This study investigated soil properties (bulk density, carbon, nitrogen, and phosphorus) in different land use types
(small scale agriculture in recent settlements, mixed agriculture in established peri-urban settlements, largescale commercial agriculture, and the gazetted forest reference condition) and their adjacent buffer strips.
Bulk density, carbon, nitrogen, and phosphorus within 30-m riparian buffer strips adjacent to recent settlement land use areas were similar to those of the gazetted forest reference condition, but only bulk density of the buffer strips adjacent to peri-urban and commercial agriculture land use areas were similar to the gazetted forest reference condition. Phosphorus is a sensitive indicator of the impacts of human activity, as increased concentrations were observed with increasing scale of land use activity. For riparian buffers adjacent to recent settlements, soil phosphorus was significantly higher in buffers narrower than 30 m (5.01 mg P kg−1) than gazetted forest (3.40 mg P kg−1) but not significantly different for riparian buffers wider than 30 m (3.81 mg P kg−1) compared to gazetted forest. Based on the research, it is recommended that policies governing riparian buffer strips become (1) stricter, with the current “maximum” of 30 m considered a minimum; and (2) adaptive, with 30 m used in small-scale agricultural areas, and wider riparian buffer strips used in medium- and large-scale agricultural areas.

Keywords: Riparian area . Buffer strip . Soil properties . River Njoro . Kenya