Assessment of the effectiveness of Payment for Ecosystem Services (PES) in the delivery of desired Ecosystem Services in Sasumua catchment, Kenya

Abstract. The study was conducted in Sasumua watershed in Nyandarua County, Kenya where a Payment for Ecosystem Services (PES) pilot project was initiated in June 2015 with the aim of promoting sustainable land management practices (SLM) that would lead to improved water quality. This study which was conducted after one year of PES implementation, seeks to establish what effect the SLM technologies being promoted under PES would have on the water quality. A representative sub-watershed was established where 42.3 ha were under intensive cultivation. Baseline status on Total Suspended Solids (TSS) was established during the rainy season of March–May 2015 just before the onset of PES project. Baseline status on SLM technologies in the study site was also established. Two V-notches were installed to record flow in the rainy season of March–May 2016 for purposes of soil and water assessment tool (SWAT) calibration. Data collection involved water sampling at selected points during two major rainy seasons of October–December 2015 and March–May 2016. Water samples were tested for TSS by photometric determination method using Lovibond water quality testing kit. The SWAT model was applied to generate two scenarios (Worst and Best scenarios) of the study site. The scenarios before and after PES project (determined from actual field measurements) were fitted in between the SWAT scenarios to evaluate the effectiveness of the PES approach after one year of PES project. The baseline status for TSS was an average of 71.05 mg/L. After one year of PES project implementation, the TSS improved to an average of 42.73 mg/L. SWAT model predicts a worst scenario for TSS at an average of 124.15 mg/L and best scenario at an average of 12.76 mg/L. Watershed management through PES approach can be effective in improving downstream water quality as shown by increase in adoption of SLM technologies from 11 % to approximately 32 % within the first year. However, long term research data is highly recommended to validate the effectiveness of PES over number of years especially on ecosystem services that manifest after long periods and establishing whether PES incentives actually maintain best conditions at farm level. More ecosystem services should also be monitored to validate the TSS results.