ABSTRACT
Aims: A personal computer version of the Stormwater Management Model (PCSWMM) was applied to seamlessly link urban runoff, sanitary flow, pump station operations, and a natural wastewater treatment wetland in Phnom Penh, Cambodia, as a step towards developing a planning tool that could be used to explore urban development or climate change scenarios. Study Design: PCSWMM was calibrated with measured flow and water quality data and used to estimate total phosphorus, total nitrogen, detergents, and E. coli levels at the outlet of the wastewater treatment wetland for the period May 15 to July 1, 2011. Place and Duration of Study: Phnom Penh, Cambodia; January, 2011 to March, 2012. Methodology: In support of model development, a limited water quality sampling program and bathymetric survey were conducted for the sewer and wetland system in both the dry and rainy seasons, 2011. Samples were analyzed for total nitrogen, total phosphorus, detergents, and E. coli. Sewer flow was measured continuously at 5 minute intervals to determine sanitary flow characteristics as input to the model and pump operation rules were determined through interviews with the pump operators and analysis of their data log books. Results: Consistent with past studies, the sampling showed that the wetland was effective in treating municipal waste, particularly with respect to E. coli (99% reduction from sewage inputs) and detergents (86% reduction from sewage inputs). A lower treatment efficiency was observed for total phosphorus, at around 31%, while the treatment efficiency for total nitrogen was around 71%. The wetland was divided into four zones and PCSWMM was run in continuous mode for the period May 2-July 1, 2011. The mean levels of E. coli, detergents, total phosphorus, and total nitrogen estimated by the model for that time period compared favorably with sample results from the field campaign in August, 2011. Conclusion: The naturally-occurring wetland treatment system in Phnom Penh is effective and fits well with the concepts of green infrastructure and eco-cities. PCSWMM is a useful decisionsupport and planning tool to explore various development and climate change scenarios in Phnom Penh.
ABSTRACT
Aims: In February and March 2014, more than 300,000 households were affected by water rationing in Kuala Lumpur, Malaysia and the surrounding State of Selangor. Further south, reservoir levels in Singapore were dropping, prompting the government to raise the water conservation rhetoric, but falling short of implementing water rationing schemes. The region experienced a dry spell that was unprecedented in the last 30 years. Preparedness for storms has been the "talk of the town" since the 2001, 2006 and 2007 extreme high precipitation events in the southern parts of the peninsula and in Singapore resulted in costly flood damage. While resilience has been a concept used frequently in climate change adaptation, it is derived from ecology, where it refers to the capacity of the system to respond to a disturbance and resist the impact or recover from the damage of the disturbance. This paper examines the case of Singapore as an urban area in responding to a similar extreme hydrologic phenomenon by examining the climate change resilience of the small city-state, with a view to recommending some considerations in designing climate change adaptation strategies. Place of Study: Singapore and peninsular Malaysia. Methodology: The paper reviews the rainfall extremes statistics covering the last 30 years for Singapore and then takes a hydrologic event-based case study approach to more closely examine the impact of record storms and the drought of March 2014 to discuss aspects of resilience that can serve as lessons for tropical cities in future adaptation to a climate-changing world. Results: Extreme rainfall events have become more frequent in Singapore over the past 30 years, while February, 2014 was the driest February since 1869. February, 2014 also had the lowest recorded daily relative humidity at 74.5%. Tropical cyclones are not expected to hit Singapore because of its location near the equator, yet Typhoon Vamei made history by delivering 210 mm of rain on 27 December, 2001. Between 19 and 20 December, 2007 Singapore received 366 mm of rain and within the same week another storm deposited 140 mm of rain in a 24 hour period. While there were some environmental and health impacts related to the February 2014 drought, including low dissolved oxygen levels in water and a localized fish kill, as well as reports of greater human respiratory problems, Singapore was able to weather the drought by requesting voluntary conservation measures, prudent reservoir management, and increasing the output of NEWater and desalinized water. Recent extreme rainfall events have produced localized flooding, but Singapore has progressively pursued a program of improved drainage, stream naturalization, and implementation of Low Impact Development (LID) technology to reduce flood-prone areas from 3,200 ha in the 1970’s to 36 ha today. Conclusion: We do not suggest that all countries need to have NEWater or desalinated water to solve drought problems. We do suggest that in managing rainfall related hazards, droughts and extremes have been treated rather independently. Based on the case study of extremes presented for Singapore we propose the importance of establishing a three-step preparedness program for extremes that includes Preparation (vulnerability and risk identification, adaptive capacity building, and monitoring), Response (information dissemination and relief action), and Recovery.
ABSTRACT
A survey of freshwater snail, Bithynia funiculata, was conducted in four locations, Doi Saket, Mueang, Saraphi and Mae Rim Districts of Chiang Mai Province, northern Thailand, between June and October, during the rainy season of 2004. A total of 2,240 snails was collected and classified into 7 families and 15 genera; of which 352 B. funiculata were obtained. B. funiculata was found most abundant in July and September. The infection rate of trematode cercariae in B. funiculata was 9.6% (19/352), while that of pleurolophocercous was 0.3% (1/352). Virgulate cercaria was the most common type, followed by lophocercous, monostome and pleurolophocercous. B. funiculata prefers habitats with clear water, which was less than 30 cm depth, temperatures between 24.48 and 31.78 degrees C, dissolved oxygen 2.03-7.66 mg/l, saturated dissolved oxygen 26.70-95.00%, conductivity 0.000-0.2642 mS/cm, turbidity 16.00-288.00 NTU and pH 6.58-7.56. Geographic Information System (GIS) analysis using loose soil mixed with clay revealed that the breeding grounds of this snail species was in the paddy fields and village environs of the Ping, Kuang and Fang river basins.