title: Trophic state assessment of global inland waters using a MODIS-derived Forel-Ule index

authors: Wang, Shenglei

subjects: Science & Technology

abstract: Eutrophication of inland waters is considered a serious global environmental problem. Satellite remote sensing (RS) has been established as an important source of information to determine the trophic state of inland waters through the retrieval of optically active water quality parameters such as chlorophyll-a (Chl-a). However, the use of RS techniques for assessment of the trophic state of inland waters on a global scale is hindered by the performance of retrieval algorithms over highly dynamic and complex optical properties that characterize many of these systems. In this study, we developed a new RS approach to assess the trophic state of global inland water bodies based on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery and the Forel-Ule index (FUI). First, the FUI was calculated from MODIS data by dividing natural water colour into 21 indices from dark blue to yellowish-brown. Then the relationship between FUI and the trophic state index (TSI) was established based on in-situ measurements and MODIS products. The water-leaving reflectance at 645 nm band was employed to distinguish coloured dissolved organic matter (CDOM)-dominated systems in the FUI-based trophic state assessment. Based on the analysis, the FUI-based trophic state assessment method was developed and applied to assess the trophic states of 2058 large inland water bodies (surface area >25 km2) distributed around the world using MODIS data from the austral and boreal summers of 2012. Our results showed that FUI can be retrieved from MODIS with a considerable accuracy (92.5%, R2 = 0.92) by comparing with concurrent in situ measurements over a wide range of lakes, and the overall accuracy of the FUI-based trophic state assessment method is 80.0% (R2 = 0.75) validated by an independent dataset. Of the global large water bodies considered, oligotrophic large lakes were found to be concentrated in plateau regions in central Asia and southern South America, while eutrophic large lakes were concentrated in central Africa, eastern Asia, and mid-northern and southeast North America.

text: Trophic state assessment of global inland waters using a MODIS-derived Forel-Ule index Eutrophication of inland waters is considered a serious global environmental problem. Satellite remote sensing (RS) has been established as an important source of information to determine the trophic state of inland waters through the retrieval of optically active water quality parameters such as chlorophyll-a (Chl-a). However, the use of RS techniques for assessment of the trophic state of inland waters on a global scale is hindered by the performance of retrieval algorithms over highly dynamic and complex optical properties that characterize many of these systems. In this study, we developed a new RS approach to assess the trophic state of global inland water bodies based on Moderate Resolution Imaging Spectroradiometer (MODIS) imagery and the Forel-Ule index (FUI). First, the FUI was calculated from MODIS data by dividing natural water colour into 21 indices from dark blue to yellowish-brown. Then the relationship between FUI and the trophic state index (TSI) was established based on in-situ measurements and MODIS products. The water-leaving reflectance at 645 nm band was employed to distinguish coloured dissolved organic matter (CDOM)-dominated systems in the FUI-based trophic state assessment. Based on the analysis, the FUI-based trophic state assessment method was developed and applied to assess the trophic states of 2058 large inland water bodies (surface area >25 km2) distributed around the world using MODIS data from the austral and boreal summers of 2012. Our results showed that FUI can be retrieved from MODIS with a considerable accuracy (92.5%, R2 = 0.92) by comparing with concurrent in situ measurements over a wide range of lakes, and the overall accuracy of the FUI-based trophic state assessment method is 80.0% (R2 = 0.75) validated by an independent dataset. Of the global large water bodies considered, oligotrophic large lakes were found to be concentrated in plateau regions in central Asia and southern South America, while eutrophic large lakes were concentrated in central Africa, eastern Asia, and mid-northern and southeast North America.

year: 2018

title: A stochastic sub-national population projection methodology with an application to the Waikato region of New Zealand

authors: Cameron, Michael Patrick

subjects: cohort-component model

abstract: In this paper we use a stochastic population projection methodology at the sub-national level as an alternative to the conventional deterministic cohort-component method. We briefly evaluate the accuracy of previous deterministic projections and find that there is a tendency for these to be conservative: under-projecting fast growing populations and over-projecting slow growing ones. We generate probabilistic population projections for five demographically distinct administrative areas within the Waikato region of New Zealand, namely Hamilton City, Franklin District, Thames-Coromandel District, Otorohanga District and South Waikato District. Although spatial interaction between the areas is not taken into account in the current version of the methodology, a consistent set of cross-regional assumptions is used. The results are compared to official sub-national deterministic projections. The accuracy of sub-national population projections is in New Zealand strongly affected by the instability of migration as a component of population change. Unlike the standard cohort-component methodology, in which net migration levels are projected, the key parameters of our stochastic methodology are age-gender-area specific net migration rates. The projected range of rates of population growth is wider for smaller regions and/or regions more strongly affected by net migration. Generally, the identified and modelled uncertainty makes the traditional ‘mid range’ scenario of sub-national population projections of limited use for policy analysis or planning beyond a relatively short projection horizon. Directions for further development of a stochastic sub-national projection methodology are suggested.

text: A stochastic sub-national population projection methodology with an application to the Waikato region of New Zealand In this paper we use a stochastic population projection methodology at the sub-national level as an alternative to the conventional deterministic cohort-component method. We briefly evaluate the accuracy of previous deterministic projections and find that there is a tendency for these to be conservative: under-projecting fast growing populations and over-projecting slow growing ones. We generate probabilistic population projections for five demographically distinct administrative areas within the Waikato region of New Zealand, namely Hamilton City, Franklin District, Thames-Coromandel District, Otorohanga District and South Waikato District. Although spatial interaction between the areas is not taken into account in the current version of the methodology, a consistent set of cross-regional assumptions is used. The results are compared to official sub-national deterministic projections. The accuracy of sub-national population projections is in New Zealand strongly affected by the instability of migration as a component of population change. Unlike the standard cohort-component methodology, in which net migration levels are projected, the key parameters of our stochastic methodology are age-gender-area specific net migration rates. The projected range of rates of population growth is wider for smaller regions and/or regions more strongly affected by net migration. Generally, the identified and modelled uncertainty makes the traditional ‘mid range’ scenario of sub-national population projections of limited use for policy analysis or planning beyond a relatively short projection horizon. Directions for further development of a stochastic sub-national projection methodology are suggested.

year: 2010-03

title: Māori academic success: Why the deficit perspectives?

authors: Aporosa, S. 'Apo'

subjects: Māori

abstract: Academics have long discussed the power of communication to both motivate and discourage. Concerning education, Paulo Freire (1997) had explained the dialogical learning process and the empowerment that comes from the inclusion of student knowledge. Alternatively, Carlson & Dimitriadis (2003) describe disempowerment and underachievement among Afro-American students resulting from societal expectations that they will fail. In a recent education environment scan focused on the Waikato-Tainui rohe, 28 kaupapa Māori education providers were identified as sites of high educational success, with one described as “outshining private schools and bucking national trends” (Carson, 2013). This aside, perceptions of generalized educational failure among Māori are commonplace in Aotearoa New Zealand. These impressions are fed by the media, the Ministry of Education (MOE) and in some cases, academic publications. This paper discusses the power of deficit models and counter-narratives to academic underachievement. This will be juxtaposed with commentary on why some students and their education providers within the Waikato-Tainui rohe appear to be unaffected by these counter- narratives and deficit theorizing.

text: Māori academic success: Why the deficit perspectives? Academics have long discussed the power of communication to both motivate and discourage. Concerning education, Paulo Freire (1997) had explained the dialogical learning process and the empowerment that comes from the inclusion of student knowledge. Alternatively, Carlson & Dimitriadis (2003) describe disempowerment and underachievement among Afro-American students resulting from societal expectations that they will fail. In a recent education environment scan focused on the Waikato-Tainui rohe, 28 kaupapa Māori education providers were identified as sites of high educational success, with one described as “outshining private schools and bucking national trends” (Carson, 2013). This aside, perceptions of generalized educational failure among Māori are commonplace in Aotearoa New Zealand. These impressions are fed by the media, the Ministry of Education (MOE) and in some cases, academic publications. This paper discusses the power of deficit models and counter-narratives to academic underachievement. This will be juxtaposed with commentary on why some students and their education providers within the Waikato-Tainui rohe appear to be unaffected by these counter- narratives and deficit theorizing.

year: 2016