Assessment of rooftop rainwater harvesting in the city of Terneuzen utilizing GIS

Abstract

Freshwater is increasingly becoming a scarce and overexploited natural resource due to rising human demand. Pressure on freshwater resources is rapidly intensifying because of climate change, population growth, and economic development. Industrial enterprises are increasingly aware of the risks posed by growing water scarcity to their operations, prompting them to explore methods to reduce their water footprint. Rooftop rainwater harvesting (RRWH) offers a potentially sustainable, cost-effective, and environmentally friendly solution for meeting industrial water needs, providing benefits such as cost savings, resource conservation, and enhanced water security.

To effectively assess the potential of RRWH for industrial use, GIS and remote sensing were used in this study to analyze the suitability of each roof. First, the slope of each roof was determined using 3D data, followed by roof type estimation through supervised classification. Based on this information, the runoff coefficient was calculated, and all roof characteristics were input into the analytical hierarchy process to visualize the spatial variability in RRWH suitability.

After determining suitability, the Getis-Ord General G statistic was applied to identify and analyze areas with high (hot spots) and low (cold spots) potential. KNMI rainfall data from 1994-2023 was then used to calculate the catchment potential of suitable roofs, and the sensitivity to KNMI's 23 climate scenarios was analyzed to assess how much RRWH could contribute to the water demand of an industrial facility in Terneuzen. Results indicate that 839 rooftops are suitable for RRWH, with 439 identified as hot spots. Even in the most unfavorable season and climate scenario, RRWH can meet 58.7% of the facility’s water demand, a substantial contribution.

The results show that GIS and remote sensing are effective methods for determining RRWH suitability and spatial variability. This study also demonstrates that RRWH can significantly contribute to sustainable water sourcing for industrial purposes, even in an increasingly uncertain climate.