Remote sensing based evaluation of uncertainties on modelling of streamflow affected by climate change

Assessment of the impacts of land-use and climate change on streamflow is vital to develop climate adaptation strategies. However, uncertainties in the climate impact study framework could lead to changes on streamflow impact. The aim of this study is to assess the uncertainties on Digital Elevation Model (DEM), Satellite Precipitation Product (SPP) and climate projection on the modelling of streamflow affected by climate changes. These uncertainties are evaluated and reduced independently. The climate projection uncertainty is addressed through the modification of the Quantifying and Understanding the Earth System - Global Scale Impacts (QUEST-GSI) methodology. Twenty-six modified QUEST-GSI climate scenarios were used as climate inputs into the calibrated Soil and Water Assessment Tool (SWAT) model to evaluate the impacts and uncertainties of climate change on streamflow for three future periods (2015-2034, 2045-2064 and 2075-2094). The selected study areas are the Johor River Basin (JRB) and Kelantan River Basin (KRB), Malaysia. The Shuttle Radar Topography Mission (SRTM) version 4.1 (90m resolution) DEM and the Precipitation Estimation from Remotely Sensed Information using Artificial Neural Networks – Climate Data Record (PERSIANN-CDR) SPP which show a better performance were selected for the SWAT model modification, calibration and validation. The results indicated that the modified SWAT model could simulate the monthly streamflow well for both basins. Land-use and climate changes from 1985 to 2012 reduced annual streamflow of the JRB and KRB by 5% and 4.2%, respectively. In future, the annual precipitation and temperature of the JRB / KRB are projected to increase by -0.4-10.3% / 0.1-11.2% and 0.6-3.2oC / 0.8-3.3oC, respectively, and that this will lead to an increase of annual streamflow by 0.5-13.3% / 4.4-18.5%. This study showed that satellite data play an important role in providing input data to hydrological models

Spatio-Temporal Analysis of Land Use Change in the Johor River Basin, Malaysia

Land use land cover (LULC) change analysis is one of the major studies around the world. Understanding the spatial and temporal changes in the historical LULC pattern is critical for impact assessment, town planning, and future LULC simulation. Johor, situated in the southern Peninsular Malaysia, is one of the most developed states in Malaysia. Johor River Basin (JRB) is the main springhead for Johor and Singapore. However, research on LULC analysis of JRB is still rarely reported. This study aims to understand the spatio-temporal changes of LULC in JRB between 1984 and 2015. The study is divided into two main parts: (1) to identify the LULC types with rapidly changes; and (2) to compute the rate of LULC changes. Three land use maps of 1984, 2002 and 2015 were collected from the PLANMalaysia agency. The results show that JRB experienced rapid growth in oil palm where the estate area expanded 47.98% from 1984 to 2015. In contrast, the forest area was decreased by 7.74% between 1984 and 2015, particularly in the southern part of JRB. Meanwhile, a significant increasing trend was found for water bodies in the northern part of the basin. This is mainly due to the construction of Linggiu Reservoir for supplying fresh water to Singapore in the early 1990s. LULC changes should be monitored and well managed to maintain the sustainability of life and water resources, by incorporating it into the hydrological model to study the future water resources of the basin

Trace metals contamination in groundwater and implications on human health: comprehensive assessment using hydrogeochemical and geostatistical methods

Monitoring the groundwater chemical composition and identifying the presence of pollutants is an integral part of any comprehensive groundwater management strategy. The present study was conducted in a part of West Tripura, northeast India, to investigate the presence and sources of trace metals in groundwater and the risk to human health due to direct ingestion of groundwater. Samples were collected from 68 locations twice a year from 2016 to 2018. Mixed Ca–Mg–HCO3, Ca–Cl and Ca–Mg–Cl were the main groundwater types. Hydrogeochemical methods showed groundwater mineralization due to (1) carbonate dissolution, (2) silicate weathering, (3) cation exchange processes and (4) anthropogenic sources. Occurrence of faecal coliforms increased in groundwater after monsoons. Nitrate and microbial contamination from wastewater infiltration were apparent. Iron, manganese, lead, cadmium and arsenic were above the drinking water limits prescribed by the Bureau of Indian Standards. Water quality index indicated 1.5% had poor, 8.7% had marginal, 16.2% had fair, 66.2% had good and 7.4% had excellent water quality. Correlation and principal component analysis reiterated the sources of major ions and trace metals identified from hydrogeochemical methods. Human exposure assessment suggests health risk due to high iron in groundwater. The presence of unsafe levels of trace metals in groundwater requires proper treatment measures before domestic use

A review of behaviour mechanisms between government and society in bargaining water pollution issues

Water pollution causes serious damage to people's lives, health and safety. As a prominent issue impacting social stability and development, protests to water pollution issues have become a great challenge for governments at all levels in recent years. This study aims to analyze the complex behaviour mechanism between participants and government, which is of great significance to the prevention and treatment of such incidents. This paper also discusses the cooperative and interactive relationship between government and society in the governance structure. In order to clarify the research progress of water pollution protest in the past decade, a systematic review has been used to identify 40 research papers related to social and governmental environmental negotiation mechanisms of water pollution events from the CNKI, SCOPUS, EIVL-LAGE2 and other databases. As a single management subject, a government can neither realize the efficiency and fairness of water resources allocation, nor effectively coordinate the contradictions among stakeholders such as the government, enterprises and the public. In order to protect the public's right to know, government must improve information disclosure, which also provides theoretical support for the government and relevant departments to control such events. Finally, the cooperative governance between government and society in water pollution events should be strengthened to improve the democratic governance ability of the government and achieve social governance innovation. Therefore, society-government cooperation should be taken as the breakthrough point, establish the concept of effective participation between government, enterprises and the public in the joint treatment of water pollution events. The study can be act as a reference for local authorities to better manage water pollution incidents with the public

Evaluation of TRMM Product for Monitoring Drought in the Kelantan River Basin, Malaysia

Assessment of satellite precipitation products’ capability for monitoring drought is relatively new in tropical regions. The purpose of this paper is to evaluate the reliability of the Tropical Rainfall Measuring Mission (TRMM) Multisatellite Precipitation Analysis (TMPA) 3B43 product in estimating the standardized precipitation index (SPI) in the Kelantan River Basin, Malaysia from 1998 to 2014, by comparing it with data from 42 rain gauges. Overall, the TMPA-3B43 performed well in the monthly precipitation estimation, but performed moderately in the seasonal scale. Better performance was found in the northeast monsoon (wet season) than in the southwest monsoon (dry season). The product is more reliable in the northern and north-eastern regions (coastal zone) compared to the central, southern and south-eastern regions (mountainous area). For drought assessment, the correlations between the TMPA-3B43 and ground observations are moderate at various time-scales (one to twelve months), with better performance at shorter time-scales. The TMPA-3B43 shows similar temporal drought behavior by capturing most of the drought events at various time-scales, except for the 2008–2009 drought. These findings show that the TMPA-3B43 is not suitable to be used directly for SPI estimation in this basin. More bias correction and algorithm improvement work are needed to improve the accuracy of the TMPA-3B43 in drought monitoring

Community Involvement in Urban Water Management: The N Park Resort Condominium Rainfall Harvesting and Water Saving Project in Penang, Malaysia

Community engagement and involvement is vital for the success of urban water management. However, poor public engagement, cheap water tariffs, apathetic attitude and lack of public interest are identified as the main reasons for high water wastage in Penang State, Malaysia. The N Park Resort Condominium rainfall harvesting and water saving project in Penang, Malaysia is a prime example of successful urban water management involving government, private sector, non-governmental organisations (NGOs) and local communities. The N-Park condominium consisting of 965 units is the first condominium in the country to initiate a community water- saving project. Started in August 2009 and completed in December 2010, the project is jointly implemented by the Drainage and Irrigation Department (DID) Malaysia (Government), Water Watch Penang (WWP) (NGO), N-Park Management Corporation (NPMC)(Community) and the Penang Water Supply Corporation (PWSC). The methodology involved installation of a rainwater harvesting system, installation of water-saving devices and a water-saving campaign. Results of the project showed that the rainwater harvesting system was most successful as the rainwater harvested was used for gardening, washing common areas and toilets, flushing toilets, and washing vehicles. The installation of water-saving devices was also successful as it resulted in substantial water savings. Results showed reduced total water usage from 8 to 25 % between September 2009 to March 2010. The greatest reduction by 50 % was between May and July 2011, followed by 47.5 % in January 2011. During the time of the project, the amount of water saved was equivalent to RM1,3971 in monetary savings per month. Over a year, this is translated to a savings of 16,818 m3 of water or the equivalent of RM 16,782. More recently, between February 2020 and April 2021, the average water saved was 5852 m3 per month or averaging 48.77 % per month, equivalent to about RM34,255. Results also showed enhanced water awareness and better relationships between neighbours. Overall, this project proved that collaboration between government-private sector-NGOs is workable, and the project can be replicated nation-wide in apartments, hotels, factories, universities, and schools

Spatio-temporal variability of droughts over the Mullaitivu District in Sri Lanka from 1980 to 2020

This research aims to evaluate the spatio-temporal changes of annual and seasonal droughts of the Mullaitivu District in Sri Lanka from 1980 to 2020 using the Standardized Precipitation Index (SPI). Four homogeneity tests were performed to identify the inhomogeneity of the monthly rainfall data obtained from twelve stations. Good quality observed data were chosen to measure SPI for determining the frequency, severity, and intensity of the drought events. This was followed by Mann Kendall's (M-K) test to analyze the drought occurrences trend. Further, the relationship between the drought events and Indian Ocean Dipole (IOD) was explored to understand how large-scale atmospheric circulation influences the local droughts. The findings show that dry periods occurred in 1982, 1998, and 2018, while 1989, 1992, 1994, 2001, 2003, 2007, and 2011 experienced severe dry phases. In addition, June, July, and August were identified as the dry months in the study area. Spatially drought over the Mullaitivu District spread from west to east, where the drought vulnerability originated in the west in March and moved eastward. A strong positive correlation (r = 0.83) between the drought events and IOD showed that IOD has considerably influenced the drought formation over the Mullaitivu District

A comparative study of different imputation methods for daily rainfall data in east-coast Peninsular Malaysia

Rainfall data are the most significant values in hydrology and climatology modelling. However, the datasets are prone to missing values due to various issues. This study aspires to impute the rainfall missing values by using various imputation method such as Replace by Mean, Nearest Neighbor, Random Forest, Non-linear Interactive Partial Least-Square (NIPALS) and Markov Chain Monte Carlo (MCMC). Daily rainfall datasets from 48 rainfall stations across east-coast Peninsular Malaysia were used in this study. The dataset were then fed into Multiple Linear Regression (MLR) model. The performance of abovementioned methods were evaluated using Root Mean Square Method (RMSE), Mean Absolute Error (MAE) and Nash-Sutcliffe Efficiency Coefficient (CE). The experimental results showed that RF coupled with MLR (RF-MLR) approach was attained as more fitting for satisfying the missing data in east-coast Peninsular Malaysia

Public Perception on Water Pricing in Penang

Increasing demand and consumption in water threatens water security and is a hindrance to achieve the Sustainable Development Goal (SDG) 6 – Clean Water and Sanitation. As a developing country, Malaysia is still highly dependent on water resources to support economic growth for agriculture, industry and domestic consumption. Penang state records the highest domestic water consumption in the country although it is considered a water-stressed state. The state government has employed integrated water management to sustain the water supply and reduce consumption. Water pricing is one of the approaches that can be used for both supply management and the control of demand management. This paper aims to examine the relationship between the demographic characteristic as factors affecting the water consumption of the Penangites with the perception of water price through a questionnaire survey. A total of 341 respondents from the north-eastern part of George Town, Penang, were randomly selected in this research. The analysis was carried out using SPSS to run the Chi-square test, whereby the p-value is used to indicate the relationship between each demographic variable with Penangites' perception of water tariff. The results show that only age and gender have a significant relationship with the perception of water price. Besides that, there is no significant relationship among education level, income and ethnicity on perception of water price. The research concludes that Penang’s water tariff could be reviewed and increased in terms of different block tariff as one of the mechanisms to reduce domestic demand and consumption

Integrating the Budyko framework with the emerging hot spot analysis in local land use planning for regulating surface evapotranspiration ratio

Land use planning regulates surface hydrological processes by adjusting land properties with varied evapotranspiration ratios. However, a dearth of empirical spatial information hampers the regulation of place-specific hydrological processes. Therefore, this study proposed a Local Land Use Planning framework for EvapoTranspiration Ratio regulations (ETR-LLUP), which was tested for the developments of spatially-varied land use strategies in the Dongjiang River Basin (DRB) in Southern China. With the first attempt at integrating the Emerging Hot Spots Analysis (EHSA) with the Budyko framework, the spatiotemporal trends of evapotranspiration ratios based on evaporative index and dryness index, from 1992 to 2018, were illustrated. Then, representative land-cover types in each sub-basin were defined using Geographically Weighted Principal Component Analysis, in two wet years (1998 and 2016) and three dry years (2004, 2009, and 2018), which in turn were identified using the Standard Precipitation Index. Finally, Geographically Weighted Regressions (GWRs) were used to detect spatially-varied relationships between land-cover proportions and evaporative index in both dry and wet climates. Results showed that the DRB was consistently a water-limited region from 1992 to 2018, and the situation was getting worse. We also identified the upper DRB as hotspots for hydrological management. Forests and croplands experienced increasingly water stress compared to other vegetation types. More importantly, the spatial results of GWR models enabled us to adjust basin land use by 1) expanding and contracting a combination of ‘mosaic natural vegetation’ and ‘broadleaved deciduous trees’ in the western and eastern parts of the basin, respectively; and 2) increasing ‘broadleaved evergreen trees’ in the upstream parts of the basin. These spatially-varied land use strategies based on the ETR-LLUP framework allow for place-specific hydrological management during both dry and wet climates