Spatiotemporal assessment of surface water vulnerability to road construction

Highway construction may pose different pollutants, including suspended solids, metals, and hydrocarbons such as oil and polycyclic aromatic hydrocarbons (PAH's) to water resources and decrease water quality. The principal contribution of this study is developing a practical approach for assessing the spatiotemporal vulnerability of surface water to road construction by using water quality data from the environmental monitoring during construction of a new 22-km-long highway in southern Norway (2017–2019). First, the data were used to assign the relative weights of parameters, and the water quality index (WQI) was computed for all monitoring stations. Then, by defining six time periods, the temporal variation of WQI in various stations was determined, and by classification of WQI in different levels (i.e., excellent water, good water, poor water, very poor water, and unsuitable for drinking), the temporal changes were analyzed. To assess the spatial variation in surface water quality during road construction, the averages of WQI in all monitoring stations of each catchment area were computed, and for each section of the road, the vulnerability map was plotted in all time periods. Besides, evaluating the impact of road construction activities on surface water quality is another innovation of this study. By extracting the activity type in each section of the road over the construction time, the average WQI for each activity was computed for all time periods. The results showed that construction activities such as blasting, area cleaning, and water management have the highest impact on surface water. The results deliver a feasible knowledge to decision-makers for establishing best management practices to control the effects of road construction on surface water bodies.