Study region: Beijing Region Study focus: Limited studies have yet been done on regionalization of multi-performances of rainwater harvesting systems (RHS). In this study, the daily rainfall records from 77 stations are used, and a hydro-economic model is adopted to examine regional water saving, stormwater control and economic performances of RHS by proposing a regionalization approach. New hydrological insights for the region: Higher water saving efficiency (WSE) and reliability (R) of RHS are linked with lower water demand, larger tank size and greater rainfall conditions. Differently, higher stormwater capture efficiency (SCE) is related to higher water demand, larger tank size and lower rainfall. The WSE and R of RHS demonstrate substantial regional differences; their maximized obtainable values closely depend on water demand scenarios and range from 9% to 99%, with smaller values in western mountain area but larger values in northeast suburban and central urban areas. The maximum obtainable values of SCE range from 61% to 100%, with higher values in western mountain area, but lower values in northeast suburban and central urban areas. A 10 m3 tank size can provide the highest benefit-cost ratio of RHS across the Beijing region. The regionalization approach proposed is a useful guidance for the implementation of RHS and sustainable urban water management, and thus it has the potential for wide uses in other regions with high rainfall gradients.

Evaluating the potential impacts of land use and land cover change (LULCC) and climate change on air pollution is crucial to unravel the driving forces and mechanisms behind changes in air quality. A multi-faceted approach was adopted, including a land change model (LCM) and Mann–Kendall (MK) test, to evaluate the transition of land cover type, changes in climate, and atmospheric pollutants during 2004–2021 in Pakistan. Moreover, a multiscale geographically weighted regression (MGWR) model and a mathematical model were used to assess the potential contribution of LULCC and climate dynamics to atmospheric pollution. It was revealed that during 2004, croplands covered an area of 9.72 × 104 mile2, accounting for 38% of the total area. However, the area of the croplands increased to 10.1 × 104 mile2, accounting for 40% of the total area in 2021. The MK test showed that the north and west–south regions significantly experienced air pollution, with the increasing trend for nitrogen dioxide (NO2) and sulfur dioxide (SO2) being 0.89× 1015 molecules/cm2 per year and 0.54 DU/year, respectively. For climate variability, mean precipitation (Precp) and mean surface pressure (SP) showed a prominent increasing trend, with a maximum value of 1 mm/year and 0.01 Kpa/year, respectively. The mean temperature maximum (Tmax) showed an increasing and decreasing trend, with the highest value of 0.28°C/year and 0.08°C/year, respectively. In the context of contribution, the conversion of cropland to grasslands increased the trend for SO2 concentrations. The highest increasing trend of 1.5 DU for ozone (O3) was found due to conversion of grasslands to shrublands. Additionally, regional climate played a significant role in making air pollution stagnant across the country. Precp and wind speed (WS) contributed significantly in escalating NO2 concentrations in Pakistan, while Precp contributed most (0.004 DU) to increasing SO2 concentrations. For O3, the most influential climate factor was Precp. These results on a long-term temporal scale demonstrated how maintaining climate variability through comprehensive land use management can help improve ambient air quality in Pakistan.

Implementation of rainwater harvesting systems (RHS) is an effective approach to tackle increasing water and energy shortages for sustainable urban development. However, water and energy saving executions of RHS are rarely explored together in cities. This study explores the water and energy saving and economic performances of RHS in the four cities (Islamabad, Lahore, Peshawar, and Khanpur) under different climate zones of Pakistan. Three water demands (lawn irrigation, toilet flushing, and their mixture) were evaluated. Results indicated that higher annual water savings of RHS were associated with larger tank-sizes and lesser water demands in humid region. Differently, higher annual energy savings of RHS were related to greater energy consumption for groundwater pumping and larger tank sizes. At Islamabad, a 20 m3 RHS can achieve 126 m3 of annual water savings and 80% time reliability for mixed water demand, but only 23 m3 of annual water savings and 10% time reliability at Khanpur. At Lahore, a 20 m3 RHS can attain 119 kWh of annual energy savings for mixed water demand, but only 20 kWh at Khanpur. The economic viability of RHS was confirmed through adequately designed RHS at Islamabad, Lahore, and Peshawar, but except Khanpur due to its lower benefit-cost-ratio than 1.0.

Rainwater harvesting is widely implemented to deal with urban water scarcity and stormwater control issues. In the context of climate change, however, the impacts of rainfall change on rainwater harvesting systems (RHS) are still unknown in many regions. In this study, effects of rainfall change on both water saving and stormwater control performance of RHS across six cities in different climatic zones of Pakistan were investigated and location-specific and adaptive measures to mitigate the negative impacts of rainfall change on RHS were proposed. The commonly defined “dry gets drier, wet gets wetter” rainfall change pattern is not retained in the cities. Water saving performance of RHS is positively affected by increasing trend of rainfall at Khanpur and Peshawar, whereas negatively affected by rainfall decreases at Zhob and Murree. Conversely, increasing trend of rainfall is non-beneficial for stormwater control at Khanpur and Peshawar but rainfall decreases are beneficial at Zhob and Murree. Islamabad and Lahore do not have notable changes in performance of RHS due to the non-significant changing trends in rainfall. The impacts of rainfall change on performance of RHS are dependent on not only the trends and extents of local rainfall change, but also tank sizes and water demands. At Khanpur and Murree, the negative impacts of rainfall change on performance of RHS can be resolved by enlarging tank sizes. At Zhob and Peshawar, however, adjusting contributing areas or water demands should also be considered. Therefore, location-specific and adaptive measures should be adopted for RHS to accommodate rainfall change.

Rainwater harvesting is broadly considered as a promising alternative water resource. In Pakistan, the availability of potable water is a significant issue due to the fast-growing population and urbanization. In this study, a hydro-economic model was developed and applied to investigate water saving and stormwater capture efficiency and financial feasibility of rainwater harvesting systems (RHS) under five climatic regions of Pakistan. Three non-potable water requirements (toilet flushing, garden irrigation, and mixture water requirements) are assessed. According to the results, stormwater capture efficiency is higher for RHS with larger tank size, supplying water for higher water requirement, and located in cities with less rainfall, whereas higher water saving efficiency and reliability are related to larger tank sizes, lower water requirement and situated in humid areas. For example, in Islamabad (humid subtropical climate), a 20 m(3) RHS can capture 33% of the stormwater for garden irrigation and achieve 84% and 88% of water saving efficiency and time reliability, respectively. In Larkana (warm desert climate) a 20 m(3) RHS achieves 33% and 32% of water saving efficiency and time reliability for toilet flushing, respectively, but it captures 61% of the stormwater. In humid subtropical, warm semi-arid and Mediterranean continental climate, the economic feasibility of RHS can be attained for appropriately designed RHS; whereas, in cold semi-arid and warm desert areas, the benefit-cost ratio is less than 1.0. (C) 2020 Elsevier Ltd. All rights reserved.