Water Agency Research Articles

The challenges of regulating water and sanitation tariffs under a three-level shared-authority federalism model: The case of Brazil

Water and sanitation regulation in Brazil shall be addressed as part of a major problem that involves institutional disputes and legal uncertainty. The paper investigates the hypothesis that the complex institutional framework plays a central role in explaining country's poor performance in the sector. Methodology is mainly qualitative, presenting an analysis that shows how political, institutional and legal hurdles play a major role in explaining the government's inability to secure a financially self-sustainable structure to the sector. The paper suggests that empowering the National Water Agency to issue general guidelines may help reducing transaction costs and fostering sector's development.

The Role of Communication in Managing Complex Water–Energy–Food Governance Systems

Managers of federal, state, local, and nonprofit organizations around the world are faced with the complex task of managing interconnected systems of scarce resources. One key example of this has been the recent research on the connections between water, energy, and food/agriculture, and the problem of managing these resources to be sustainable and reduce the likelihood of resource depletion. While engineering research has focused on achieving greater efficiencies in resource management, less attention has been given to issues of governance within the fragmented, decentralized, and polycentric systems that are responsible for resource delivery. The central question animating this paper is whether resource management decisions in water, energy, and food are siloed, and what theoretical frameworks can be leveraged to develop strategies to break down existing silos. Results from a survey of water agencies suggests that there is little communication between the water, energy, and food policy areas. If achieving greater nexus requires increased communication and repeated interactions, there is significant work to be done to re-think how policy and management are organized and conducted.

Monitoring and Evaluation of Rural Water Supplies Sustainability in Ghana

Sustaining functionality and service levels of rural water systems in Ghana remains fraught with difficulties and can undermine the achievement of sustainable development goal six. The aim of this article is to contribute to emerging literature on monitoring and evaluation by assessing rural water system functionality, service levels and performance of service providers and authorities, particularly in terms of compliance to the Community Water and Sanitation Agency norms and standards. While more than three quarters of handpumps and piped schemes are functional, only 5% handpumps and 22% piped schemes provide basic services. Service providers have challenges in the area of composition, bank accounts, up-to-date financial and operational records, routine maintenance, and water quality testing in line with national guidelines. The study found that only one service authority carried out regular monitoring support toservice providers for small communities. This study highlights how systematic monitoring of rural water facilities, service providers and authorities provide information necessary to plan, set targets, budget , monitor progress , take remedial action and ensure accountability and sustainability of services. This article argues the need for stronger and regular post-construction support such as monitoring and evaluation and capacity building for service providers and authority to safeguard sustainable waterservices.

Transparência da informação pública no Brasil: uma análise da acessibilidade de Big Data para o estudo das interfaces entre mudanças climáticas, mudanças produtivas e saúde

A informação pública, garantida por lei no Brasil, é base para a geração de conhecimento adaptativo em situações adversas, como a extrema vulnerabilidade socioambiental e seus impactos na saúde humana. O presente artigo avalia a transparência da informação pública nas áreas de saúde humana (com foco no Sistema Único de Saúde – SUS), mudanças produtivas (uso do solo) e mudanças climáticas (chuva e temperatura), utilizando dados de 5.570 municípios brasileiros, ao longo dos últimos 20 anos. A experiência da construção de uma base nacional de dados (Data Lake) a partir de informações disponibilizadas em bases públicas (ou público-privadas) – DATASUS, MapBiomas, Instituto Nacional de Meteorologia (Inmet) e Hidroweb da Agência Nacional de Águas (ANA) – confimou que, na prática, a acessibilidade da informação pública no Brasil apresenta entraves importantes. Incluímos recomendações sobre como ela pode ser aprimorada para tornar os direitos de acesso à informação uma realidade mais concreta para o cidadão brasileiro.

Sustainable Water Resource Management: Multistakeholder Engagement Approach: A narrative Review

Fresh water resources and limited across the globe. They are threatened by agriculture, economic development and climate change. Measure to sustainably manage water resources are not well documented. This review aimed at analyzing publications from 2000-2019 regarding stakeholders’ involvement as a key for sustainable water resource management. Literature search was conducted using key words: integrated water resource management; transboundary water resource management; collaborative water resource management; Multistakeholder water resource management; challenges and opportunities of water resource management; domestic water saving; sustainable water resource management from Science Direct database, ResearchGate professional network and Google School Search engine. 280 publications were retrieved from which 150 were found relevant, were read and used during the publication of this paper. It was found that climate change, population explosion, economic development all threaten water resources management and involvement of all stakeholders, transboundary agreements, collaboration with international water agencies and financial investment were recommended for sustainable water resource management.

Technological enablers and confidence building in end-users for effective non-domestic water demand management

ABSTRACT By 2060, 70% of Singapore’s total water demand will be used for non-domestic purposes. Effective management of this demand will allow the national water agency, PUB, to achieve significant leverage and take strides in water sustainability as land use nears capacity limits in Singapore. Uptake of water conservation projects was sluggish in the initial years due to the high upfront capital and manpower resources required for implementation, and perceived incremental benefit to business margins. Through policy reform, technological innovation and a rigorous industrial engagement strategy, PUB has since completed 45 water conservation projects and is set to achieve 14.3 million gallons per day in non-domestic water savings by the end of 2020.

Análise da variabilidade da precipitação frente às mudanças no uso da terra no município de Tucuruí-PA

O objetivo do presente estudo foi analisar as variações da precipitação e a dinâmica espacial do uso e cobertura da terra no município de Tucuruí, Pará, Brasil, no período de 1980 a 2015. Para isso, foram utilizados dados das estações meteorológicas do Instituto Nacional de Meteorologia (INMET) e da Agência Nacional de Águas (ANA). Para o estudo da precipitação no município foram utilizados testes de Mann-Kendall e Sen's Slope com nível de significância de 95%. Para compreender as mudanças da cobertura da terra na área de estudo, utilizou-se o modelo linear de mistura em imagens Landsat-TM 3, 5 e 8 segmentadas, para análise multitemporal das classes da cobertura da terra identificadas no município. Os resultados indicaram que não houve tendências nas séries dos totais anuais de precipitação (1980 a 2015). Porém, constataram-se significativas variações do regime de chuvas interanuais, com precipitação média anual de 2431.6 mm. Os dados indicaram sazonalidade caraterizada por duas estações distintas: (1) menos chuvosa, entre os meses de junho a novembro; e (2) mais chuvosa, entre os meses de dezembro a maio. O mapeamento mostrou diferentes classes de uso da terra no período estudado, no entanto, as classes da vegetação nativa, vegetação secundária, hidrografia e solo exposto apresentaram variação espaço-temporal não linear. Contudo, a classe do solo exposto exibiu um comportamento crescente desde 1980, com o início das obras da usina hidrelétrica. Em relação à precipitação anual do município, nota-se que não há relação direta com as classes do uso e cobertura da terra nos anos analisados.

Variability and Trend of Air Temperature and Rainfall at Ribeirão do Lobo Hydrographic Basin, Brazil

Climate changes have been observed all over the world and are pointed out as responsible to impact the natural resources, especially the amount and the quality of the water in a hydrographic basin. Thus, the present research aimed to analyze the variability and trends of air temperature and rainfall data in the Hydrographic Basin of the Ribeirão do Lobo, São Paulo state, Brazil. The weather data from 1988 to 2017 were collected in the Center of Water Resources and Environment Studies of the University of São Paulo (CRHEA), and in five rainfall stations of the National Water Agency of Brazil (ANA) spread all over the basin. To identify climate changes were applied the simple regression, the run test, the Mann-Kendall and modified Mann-Kendall tests. The results showed significant positive trends in air temperature, especially in the annual period and during the third quarter with rising up to 0.068 °C year-1. Significant increases were verified to minimum, maximum and mean air temperature, which suggests possible climate changes during the period in the analysis. To the rainfall data, periods with positive and negative trends were found, although, most of the time the trends were non-significant. However, a significant negative trend of the rainfall was observed in Ribeirão do Feijão station with a reduction of -10.03 mm year-1. Variabilidade e tendência da temperatura do ar e precipitação na Bacia Hidrográfica do Ribeirão do Lobo, Brasil R E S U M OAs mudanças climáticas têm sido observadas em todo o mundo e são apontadas como responsáveis por impactar os recursos naturais, especialmente a quantidade e a qualidade da água em uma bacia hidrográfica. Assim, o presente trabalho teve como objetivo analisar a variabilidade e as tendências da temperatura do ar e da chuva na Bacia Hidrográfica do Ribeirão do Lobo, Estado de São Paulo, Brasil. Os dados meteorológicos de 1988 a 2017 foram coletados no Centro de Recursos Hídricos e Estudos Ambientais da Universidade de São Paulo (CRHEA), e em cinco estações pluviométricas da Agência Nacional de Águas do Brasil (ANA) distribuídas por toda a bacia. Para identificar as mudanças climáticas, foram aplicados os testes de regressão simples, teste de run, Mann-Kendall e Mann-Kendall modificado. Os resultados mostraram tendências positivas significativas na temperatura do ar, especialmente no período anual e durante o terceiro trimestre, com aumento de até 0,068 °C por ano. Aumentos significativos foram verificados para temperatura mínima, máxima e média do ar, o que sugere possíveis mudanças climáticas no período analisado. Para os dados de chuva, foram encontrados períodos com tendências positivas e negativas, contudo, na maioria das vezes, as tendências não foram significativas. No entanto, uma tendência negativa significativa da precipitação foi observada na estação de Ribeirão do Feijão com redução de -10,03 mm ao ano.Palavras-chave: mudanças climáticas, regressão simples, Mann-Kendall, tendência.

Multivariate assessment of groundwater quality in the basement rocks of Osun State, Southwest, Nigeria

Groundwater is a major source of drinking water in many rural and urban areas of developing nations. Pollution of groundwater from diverse sources is an issue of concern due to inherent health problems. This study assessed the possible contamination source to groundwater quality in the basement rocks of Osun State, South-Western Nigeria using multivariate analyses of Principal Component Analysis (PCA) and Cluster Analysis (CA). The secondary data from 536 wells across the 30 Local Government Areas in the State were collected from the Rural Water and Environmental Sanitation Agency (RUWESA). The groundwater data include pH, temperature, turbidity, oxido-reduction potential, total dissolved solids, electrical conductivity, total alkalinity, magnesium hardness, calcium hardness, total hardness, free chlorine, total chlorine, chloride, fluoride, nitrate, nitrite, iron, manganese and zinc. The data were subjected to simple and inferential statistics using the Statistical Package for Social Sciences (SPSS vs. 21.0). The mean results of groundwater parameters such as nitrate and Mn were higher than the World Health Organisation (WHO) limits of 0.4 and 10 mg/L, respectively. The results of the PCA and CA revealed possible sources of pollutants to the groundwater quality as weathering of bedrocks, leachate from septic tanks and dumpsites, runoff of materials, hardness, nutrients from agricultural lands, and chlorine pollution.

PROBABLE RAINFALL OF DIVINÓPOLIS CITY, MINAS GERAIS STATE, BRAZIL

The aim of this paper was to analyze the behavior of non-parametric statistical distributions on the prediction of probable monthly and total annual rainfall as well as to determine the monthly and annual probable rainfall with different levels of probability for Divinópolis, Minas Gerais State, Brazil. The analysis consisted in adjusting the theoretical probability distribution to a data series of 66 years of monthly and annual rainfall. The data were obtained from the Hidroweb service, controlled by the National Water Agency (ANA, in Portuguese). The frequency distributions of Gumbel for Maximus, Fréchet and Gamma were adjusted to the observed series, where the adherence of these models to the data were tested by the Kolmogorov-Smirnov and Chi-Squared test, both with 5% of probability. The model that best represented, in most cases, the frequency distributions of the series of total monthly precipitation was Gumbel for Maximus, while the Fréchet model had the worst result, not fitting to the data of the historical series for both tests performed in the study. The probable monthly maximum precipitation for Divinópolis is 527 mm, associated with a probability of 5% and for January, while the lowest one is 0.0042 mm, with probability of 95% in July.

Chemical fractionation and risk assessment of trace elements in sewage sludge generated from various states of Pakistan.

In the developing world, rapid urbanization and industrialization produces an enormous volume of wastes daily. This study was aimed to explore the potential and risks associated with sewage sludge through the characterization and fractionation technique. Sewage sludge samples were collected from various wastewater treatment in five different cities of Pakistan. Considerable amounts of macro-elements were detected in all types of sewage sludge samples. The pHw of all sewage sludge were neutral to slightly alkaline in reaction. Total organic carbon (TOC) was maximum (18.73%) with Coca-Cola sewage sludge (CSS) while the minimum (14.69%) was with Water and Sanitation Agency (WASA) sewage sludge (WSS). Percent relative distribution of cadmium (Cd) was higher in residual fraction (F4) up to 52% in the Nestle wastewater treatment plant, Sheikhupura (NSS). The chromium (Cr) concentration in Kasur sewage sludge (KSS) was extremely in mobile fraction (exchangeable) as compared with all other sludge samples, therefore showing a higher level of risk assessment code. While in the case of Iron (Fe), mobility was less and its maximum portion was noted in residual fraction (F4) of all sewage sludge samples. Percent distribution of manganese (Mn) showed variable trends for different sewage sludge samples. Zinc (Zn) concentration showed high mobility (exchangeable fraction) in case of NUST wastewater treatment plant, Islamabad (NTS) (31.16%) and WSS (37.83%) as compared with other sewage sludges. The risk assessment code indicated that Zn and Ni had a medium level of risk with I-9 Sector wastewater treatment plant, Islamabad (ISS), CSS, KSS, and NSS whereas these pose a high risk with NTS and WSS. Based on physicochemical properties, nutrients, trace elements, mobility, and risk assessment code, it was concluded that KSS should not be recommended at any application rate while NTS and WSS may be used at low application rates whereas ISS, CSS, and NSS may be used for agricultural crop production.

Water Safety Planning and Implementation in a Ghanaian Small-scale Water Supply System

This study looked at the Assin Fosu Small Town Water Supply System in Ghana to verify whether the operation of the scheme is based on a comprehensive water safety plan and how the practice of water safety planning affects the quality of water delivered to the consumers. The study employed document reviews, structured observations, interviews and laboratory analysis of water samples. System design data files and an Operation and Management Contract document were reviewed along with in-depth interviews with key stakeholders of the water supply system. Structured observations were made to assess the management practices of the system managers. Three rounds of sampling of water were done at monthly intervals from 10 randomly selected public standpipes, 3 boreholes and 2 filtration units. Samples were analysed to assess their bacteriological safety and aesthetic (physical) quality (turbidity and colour). Upon detection of bacteriological contamination, the adequacy of disinfection was assessed by measuring the levels of residual chlorine. It was found that the recommended schedule for some key documented water
 quality control and monitoring activities were not complied with. Consequently, the quality of water delivered to consumers at several public standpipes failed to meet the WHO guidelines for drinking water. Forty percent (40%) of all samples were found with faecal contamination, with 60% and 50% exceeding the WHO’s guideline levels for turbidity and colour respectively. It is recommended that the Community Water and Sanitation Agency in Ghana intensifies on-going efforts at ensuring that small-scale water supply systems in the country are managed with comprehensive water safety plans to prevent microbial contamination which could pose significant health risks to the consumers.

Disadvantaged communities and drinking water: a case study of Los Angeles County

This paper discusses the challenges facing urban water systems in disadvantaged communities (DACs) using Los Angeles County as a case study area. We review issues of water contamination and rising water costs in the context of a highly fragmented and variable landscape of community water system sizes, types and available resources. A consideration of available state aid follows, including earmarks for disadvantaged communities, the criteria for qualifying as such, and the process of documenting disadvantaged status. We then present a useful data-driven technique for estimating the median incomes of community water system service areas. Examination of these case study results shows: (1) many local pockets of poverty cannot qualify as disadvantaged communities under current California laws and regulations; (2) extreme geographic concentrations of disadvantaged systems and class-based segregation call into question both the policy of agency consolidation and the presumptions of economies of scale on which it rests, and (3) Urban systems that are now potentially eligible for funds as DACs have far more difficulty than rural systems documenting their low median incomes due to complex and fragmented census geographies. We recommend applying our technique statewide to pre-qualify DAC water systems for state assistance, thus removing much uncertainty and risk for community water agencies considering applying for state funds.

Patterns of fish communities and water quality in impounded lakes of China's south-to-north water diversion project

Understanding the ecological impacts of large-scale hydraulic projects is critical for maintaining ecosystem health while meeting human water needs. It is, however, currently hindered by a lack of direct evidence on ecological impacts associated with this type of project particularly on water quality and fish communities. Here, we characterized patterns and variations of fish communities and water quality in five impounded lakes of the Chinese South-to-North Water Diversion Project (SNWDP), with the aim of better understanding potential ecological impacts of inter-basin water transfers. We found that 1) the impacts of water transfer on water quality in the impounded lakes was generally characterized by hydrological parameters (e.g. total suspended solids, turbidity, transparency, chlorophyll a, dissolved oxygen, conductivity and total hardness) in an upstream-downstream direction; 2) increased hydrological connectivity may have favored biological invasion (e.g. Tridentiger bifasciatus) and promoted a potential biotic homogenization among the impounded lakes; and 3) there was a pattern of decreased fish abundance and biomass from the upstream to downstream lakes with fish communities strongly driven by changing water quality patterns across the impounded lakes. These findings improve our understanding of ecological impacts of large-scale hydraulic projects and provide a significant basis for water agencies with similar water transfer systems to optimize their water transfer management in order to minimize ecological impacts.

Statistical modelling of French drinking water pipe inventory at national level using demographic and geographical information

Abstract At the request of the French Ministry for Ecological and Inclusive Transition (MTES) and the French Biodiversity Agency (AFB), INRAE carried out a study focusing on the creation of a national asset knowledge base for drinking water networks, operating at Water Agency (WA) scale. Our study involved the creation of a number of statistical models. These models combine data relating to network characteristics (gathered from a sample of utilities) with geographical and demographical data collected from all municipalities in France. The SISPEA database, along with GIS data from a sample covering around half of the total French drinking water network, were used to configure multi-linear pipe models by diameter, installation period and type of material. On the basis of these models, the total length of drinking water pipes in mainland France was estimated to be 875,000 km. Networks are quite young (60% of the total length was laid after 1970), small diameter pipes are the majority (70% of the pipes have a diameter less than or equal to 100 mm) and the materials used are linked on geographic areas (pipes are mainly made of PVC in the west of France while cast iron pipes predominate in the other regions).

When the Well Runs Dry: Groundwater Policy and Sustainability Post–Agua Caliente

Author(s): Tyra, Alec D. | Abstract: In the height of a seven-year drought in California, The Agua Caliente Band of Cahuilla Indians (the Tribe) sued the Coachella Valley Water District and Desert Water Agency (Together as “Water Districts”) to secure their right to groundwater stored in the Coachella Valley Aquifer (Aquifer). The Aquifer, like most groundwater resources in California, was severely taxed during the drought. This forced California to respond by passing the Sustainable Groundwater Management Act (SGMA), the first groundwater regulation in the State’s history. SGMA requires “sustainable groundwater management” for all basins by creating Groundwater Sustainability Plans (GSPs). These plans are, in effect, stakeholder negotiations on basin management. Basin adjudications will likely occur if these negotiations break down. In Agua Caliente Band of Cahuilla Indians v. Coachella Water District, the Ninth Circuit became the first federal court to expand the definition of Winters rights to include groundwater. Winters rights are federally reserved rights to water to help sustain the primary purpose of a federal reservation. The expanded definition of Winters rights increases the bargaining power of tribes, as stakeholders, in the GSPs and any possible basin adjudication. This decision greatly impacts California and other states in the Ninth Circuit. It would also have major implications for Arizona if Arizona had not been managing groundwater in much of the state since the 1980s. Additionally, Arizona recognized a tribal right to groundwater in Gila III in 1999. Agua Caliente affects the future of water supplies by broadening the definition of federally reserved rights to include tribes’ right to groundwater. This Comment recommends that private and public stakeholders across the West follow Arizona’s lead with respect to water planning in the Ninth Circuit’s jurisdiction by using settlement agreements with tribes to secure contested supplies of groundwater.

Energy use for urban water management by utilities and households in Los Angeles

Reducing energy consumption for urban water management may yield economic and environmental benefits. Few studies provide comprehensive assessments of energy needs for urban water sectors that include both utility operations and household use. Here, we evaluate the energy needs for urban water management in metropolitan Los Angeles (LA) County. Using planning scenarios that include both water conservation and alternative supply options, we estimate energy requirements of water imports, groundwater pumping, distribution in pipes, water and wastewater treatment, and residential water heating across more than one hundred regional water agencies covering over 9 million people. Results show that combining water conservation with alternative local supplies such as stormwater capture and water reuse (nonpotable or indirect potable) can reduce the energy consumption and intensity of water management in LA. Further advanced water treatment for direct potable reuse could increase energy needs. In aggregate, water heating represents a major source of regional energy consumption. The heating factor associated with grid-supplied electricity drives the relative contribution of energy-for-water by utilities and households. For most scenarios of grid operations, energy for household water heating significantly outweighs utility energy consumption. The study demonstrates how publicly available and detailed data for energy and water use supports sustainability planning. The method is applicable to cities everywhere.

Lifelong Learning in the Water Sector

Danas, krajem druge dekade 21. stoljeća, 900 milijuna ljudi – gotovo sedmina svjetske populacije, nema pristup dovoljnim količinama higijenski ispravne vode za piće. S ubrzanim rastom stanovništva u svijetu, rastom urbanizacije, povećanom eksploatacijom šumskih površina i već prisutnim efektima klimatskih promjena ovaj problem postaje sve veći i na globalnoj razini sve je teže osigurati i održati adekvatne količine vode. Nasreću, Hrvatska je peta zemlja u Europi po zalihama pitke vode, no, nažalost, preko 50 % vode koja ulazi u vodoopskrbne sustave na putu od izvorišta do krajnjeg korisnika gubi se zbog istjecanja iz mreže. Naravno, gubitak za život i zdravlje najvažnijeg svjetskog resursa, osim bioloških, ima i značajne financijske posljedice koje se odnose na povećanje crpljenja i proizvodnje vode, kako bi se kompenzirali gubitci, što neminovno pridonosi neopravdanom povećanju cijena vode. Državna agencija Hrvatske vode prošle godine izdvojila je 100 milijuna kuna za rješavanje problema prevelikih gubitaka u vodovodima, od kojih je samo polovica utrošena, dok polovica sredstava nije iskorištena. Uzimajući u obzir bioetički kontekst problema, rad ima nekoliko zadaća: (1) naglasiti potrebu uspostave kontinuiranog cjeloživotnog obrazovanja i usavršavanja u vodnom gospodarstvu; (2) naglasiti žurnost njegove organizacije za najširu bazu srednje stručne spreme koja radi u vodnom sektoru, a koja danas nema praktički nikakve mogućnosti usavršavanja; (3) dokazati da ulaganje u skupu i naprednu opremu bez paralelnog podizanja nivoa znanja u komunalnom sektoru nije racionalno; (4) ukazati na to da cjeloživotno obrazovanje djelatnika u vodnom sektoru treba biti popraćeno adekvatnim prijevodima literature koje na svjetskim jezicima ima u izobilju; (5) raditi na edukaciji najmlađih kako bi ih se na vrijeme upoznalo s važnosti vode kao jednog od najvažnijih resursa na Zemlji; (6) ukazati da treba paralelno upoznati sve korisnike sustava vodoopskrbe, odvodnje i pročišćavanja otpadne vode o načinima štednje vode i pravilnog korištenja sustava vodoopskrbe, odvodnje i pročišćavanja otpadnih voda. Naravno, očuvanje vodnog resursa usko je povezano s podizanjem bioetičke svijesti i znanja o važnosti vode kod svih korisnika; uvjerenja smo da se samo cjeloživotnim obrazovanjem i višedimenzionalnim usavršavanjem djelatnika koji rade u vodnom sektoru mogu postići najbolji rezultati. Rečeno nije samo ekonomski imperativ, nego prije imperativ oživljavanja skrbi za život.

Risk Management of Cyanotoxins in Singapore

Cyanotoxins produced by cyanobacteria pose significant challenges to water resource management due to the potential impacts they have on human health. Cylindrospermopsin (CYN) and microcystins (MC) are the more commonly detected cyanotoxins in Singapore’s reservoirs. Among the MC congeners monitored locally, the most frequently detected variants are MC-RR (37.6%), followed by MC-LR (25.6%). MC-LA and MC-YR are the least frequently detected variants (7.1%). No cyanotoxins have been detected in Singapore’s treated drinking water. Singapore’s National Water Agency (PUB) and the National Environment Agency (NEA) developed recreational water quality guidelines using Chl a concentrations of 50 μg/L. In local surface waters, long-term data showed that at 50 μg/L of Chl a, MC-LR concentrations ranged from a concentrations, Microcystis cell counts in reservoir water have also been used to manage cyanotoxin risk in drinking water. Specifically, routinely monitored data from all 17 Singapore reservoirs indicated that to keep MC-LR concentrations below the WHO provisional guideline of 1 μg/L in drinking water, Microcystis cell counts needed to be Microcystis isolates showed M. aeruginosa produced the most MC compared to M. ichthyoblabe, M. flos-aquae, and M. viridis. Based on the maximum toxin cell quota equivalent to the WHO provisional guideline for MC-LR of 1 μg/L in drinking water, a 5000 cells/ml cell count guideline was derived for M. aeruginosa. This cell count has also been incorporated into Singapore’s cyanotoxin risk management framework for reservoirs.

Alternative model of intense rainfall equation obtained from daily rainfall disaggregation

ABSTRACT The objective of this work was to propose an alternative model of IDF equation based on the disaggregation of daily rainfall. Data from the rainfall gauge station code 02649018 of the Brazilian National Water Agency from the period 1968 to 2011 were used. Several extreme event probability distributions were adjusted. Rainfall intensity with a return period of 2 to 100 years and durations of 5 to 1440 minutes were estimated using the relationships between rainfall for different durations. The four coefficients of the traditionally used IDF equation were adjusted, obtaining a sum of squares of deviations equal to 695.1 (mm.h-1)2 and standard error of estimation equal to 2.69 mm.h-1. For the model of the intense rainfall equation proposed, that relates the rain intensity and duration with the maximum daily rainfall, the sum of squares of the deviations was 33.6 (mm.h-1)2 and the standard estimated error was 0.59 mm.h-1. Including the return period in the model, we obtained squares of the deviations of 129.4 (mm.h-1)2, with a standard error of estimation of 1.16 mm.h-1. The models proposed have, besides better estimation accuracy, the advantages of facilitating the updating only by updating the maximum daily precipitation and sub serve the spatial representation.