Evaluating the Hydrological and Erosional Benefits of Afforestation Interventions in Ayubia National Park, Pakistan: Implications for Groundwater Recharge and Sediment Yield Reduction
Hafiz Sajid Hussain1 
, Muhammad Waseem2* , Najam Ul Hassan1 ,
Muhammad Madnee3 , and Nugraha Akbar Nurrochmat4
Abstract. The effects of deforestation on hydrological services and stability of soil are a major concern in the mountain areas. This study quantitatively evaluates the benefits of afforestation interventions on groundwater recharge and sediment yield in the sensitive ecosystem of Ayubia National Park, Pakistan. A comparative watershed study was used, evaluating four watersheds (two afforested "treated" and two degraded "untreated"). Field measurements were made of infiltration capacity (double ring infiltrometer), stream discharge (velocity-area method), and sediment yield (fixed area plots). Findings showed treated areas yielded significantly higher infiltration capacity (up to 40 mm/h) as compared to untreated (p < 0.001). The average stream discharge after rainfall in vegetated watersheds increased moderately by 25% as compared to a 92% increase in an untreated watershed indicating great flood-mitigating ability of vegetated watersheds. In addition, sediment yield was about 50% lower in treated areas. Vegetation cover (trees, shrubs, grass) was determined to be the most significant determinant of improved soil porosity and infiltration by multivariate regression analysis. The conclusion drawn by the findings is quite clear and as per the requirements, afforestation is found as one of the key nature-based solutions for managing water resources sustainably and improving groundwater recharge, mitigating floods and reducing erosion in the vulnerable watersheds of the Himalayan region.
Keywords: deforestation, watershed management, nature-based solutions, land use change, infiltrometer and discharge flow