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[Display omitted] • Groundwater vulnerability zonation investigation is conducted for GHM Greater Bay Area. • Three different perspectives are comprehensively considered in this study. • Groundwater risk, function value and contamination status are superposed using the AHP method. • Quantification and visualization of groundwater contamination prevention regionalization. • The AHP-DRASTICH model is an effective method to evaluate the groundwater risk in shallow aquifers. The groundwater contamination assessment and prevention regionalization are an important part of groundwater investigation, which is of great significance to groundwater environmental management and contamination control. Although the Guangdong-Hong Kong-Macao Greater Bay Area (GHM Greater Bay Area) has faced significant groundwater contamination since 2020, there's been no investigation into its vulnerability zonation. In this paper, groundwater in a typical area of south China was taken as the research object. We analyzed groundwater contamination risk by considering both the groundwater vulnerability and the load from contamination sources. Using the analytic hierarchy process (AHP) method, we superposed the groundwater risk, function value and contamination status, and realized the quantification and visualization of groundwater contamination prevention regionalization. Based on the DRASTIC model, the zones of low, moderate, high, and very high vulnerability are respectively 14.2 %, 24.28 %, 37.67 %, and 20.45 % of the study area. Results show that the groundwater vulnerability grade in the area is III-IV, which means it is easy to be polluted. The functional value of groundwater in the south-central part of the region is relatively high. Most of the areas with high prevention and control levels are located in plain areas and the Piedmont plain area with an area of 460 km2. The secondary control levels (key protection area) are mainly located in the middle, southwest, and northeast of the plain, with an area of 6944 square kilometers. Consequently, the ideas and contamination prevention zone maps might provide a scientific foundation for long-term planning and management and groundwater conservation in the Guangdong-Hong Kong-Macao Greater Bay Area and peripheral zones. [ABSTRACT FROM AUTHOR]

• ERA5 describes moderate-intensity rainfall, but fails for hourly/daily precipitation. • ERA5-HRES outperforms ERA5-Land in detecting rainfall magnitude and rainfall events. • ERA5 performs best in coastal cities and mountainous vegetation areas during the wet and dry season, respectively. • ERA5 is insufficient in reproducing precipitation in areas with high urbanization level. Precipitation is an important component of the global water cycle. A comprehensive understanding of precipitation characteristics, especially that in urban areas, is essential for practical applications in hydrology. ERA5, a state-of-the-art reanalysis product with wide temporal coverage as well as fine spatial and temporal resolution, has greater potential to reproduce precipitation than many other products. However, how ERA5 precipitation performs has not been well investigated in urban areas. Therefore, we evaluate and compare the ability of two ERA5 products, ERA5-Land and ERA5-HRES, in the Guangdong-Hong Kong-Macao Greater Bay Area (GBA) using observations from over 3000 rain gauges in a high-density network during 2018. The results show that ERA5 products generally characterize moderate-intensity rain. Due to the different causes of seasonal precipitation as well as the combined influence of coastal effects and topography, the best performance of ERA5 products is found in the southern coastal plains during the wet season and in the northern mountainous vegetation areas during the dry season. Meanwhile, it is challenging for ERA5 products to model precipitation in areas with higher urbanization levels. We also find that ERA5-Land data with finer spatial resolution fails to deliver any preferable results than ERA5-HRES. ERA5 products needs further improvement in the GBA for providing accurate precipitation patterns. This paper gives a detailed insight into the performance of ERA5 products, which offers a valuable reference for its probable applicability in the coastal urban areas. [ABSTRACT FROM AUTHOR]

• A spatial-temporal rain field generator is developed to reproduce regional rainfalls. • The generator produces likely future rainstorm scenarios considering climate change. • Correlations among temporal process parameters and different stations are considered. • Rain extremes may increase notably at the end of 21st century in Greater Bay Area. A stochastic rainfall generator is required to provide rainfall inputs for the analysis and mitigation of such hydrological or geologic hazards as floods and rain-induced landslides. This paper presents a new spatial-temporal rainstorm generator for generating simultaneous rainfall processes at numerous locations considering the spatial correlation among these locations and interpolating the point processes into an areal rain field. The generator is able to include the effect of climate change by adjusting the parameters of the marginal distributions of variables constituting rainfall events. A case study on the Guangdong-Hong Kong-Macau Greater Bay Area (GBA), one of the regions that are most prone to storm-related disasters in the world, is presented. The performance of the proposed generator is excellent in reproducing the historical statistical characteristics of regional rainfall. The model is adapted to climate change through extrapolation of the variation trend of the model parameters in the observation period to explore possible future scenarios of regional rainfall in GBA. The simulation results indicate a significant increase in rainfall extremes, especially for short-duration rainfall, at the end of 21st century in GBA. [ABSTRACT FROM AUTHOR]

• Hong Kong's municipal water footprint (WF) is 326 l/cap/d. • Its indirect water use (or WF) due to food consumption is 4727 l/cap/d. • Hong Kong has a typical urban diet, with too high animal product consumption. • Some products consumed in Hong Kong contribute to blue water scarcity. • Citizens of Hong Kong can reduce water resource use by changing their diets. During the last years, the city of Hong Kong has made large investments to make its urban water supply system more water efficient and sustainable. As such, its municipal water abstraction – often defined as direct water use – has decreased from 355 litre per capita per day (l/cap/d) in 2005 to 326 l/cap/d in 2013. Due to its political history, Hong Kong is unique in the world in data availability on urban food consumption. It is therefore the ideal case study to show typical urban food consumption behaviour and its related indirect water use. The objective of this paper is to show the large water quantities associated with indirect water use and that the citizens of Hong Kong can additionally save much more water by looking at this indirect water use. The current average diet in Hong Kong is very different to the average Chinese diet. It is characterised by a high intake of water intensive products like animal products and sugar, leading to a food related indirect water use or water footprint (WF cons) of 4727 l/cap/d. According to recommendations from the Chinese Nutrition Society for a healthy diet, the intake of some product groups should be increased (vegetables and fruit) and of other product groups reduced (sugar, crop oils, meat and animal fats). This would result in a reduction of the WF cons of 40% to 2852 l/cap/d. Especially the reduced intake of meat (including offals) from currently 126 kg per capita per year (kg/cap/yr) to the recommended value 27 kg/cap/yrwould results in a substantial WF cons reduction. Meat consumption in Hong Kong is extremely high. A pesco-vegetarian diet would result in a reduction of 49% (to 2398 l/cap/d) and a vegetarian diet in a 53% (to 2224 l/cap/d) reduction. Hong Kong citizens can thus save a lot of water through a change in their diet. Many of the products consumed, contribute to different levels of blue water scarcity in the regions of origin Hong Kong imports from. This poses a water-related risk to food security in Hong Kong. As all diet scenarios also result in a lower blue WF cons , they decrease this risk. In order to become sustainable, (mega)cities should reduce their dependency on distant resources and ecosystems. [ABSTRACT FROM AUTHOR]