Martin Kappas

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Papers by Martin Kappas

Evaluating SWAT model for streamflow estimation in the semi-arid Okavango-Omatako catchment, Namibia

African Journal of Environmental Science and Technology, Nov 30, 2022

A semi-distributed hydrological model was used for runoff estimation in the Okavango-Omatako catc... more A semi-distributed hydrological model was used for runoff estimation in the Okavango-Omatako catchment in Namibia. The model was configured for a 31-year period from 1985 to 2015. Subsequently, calibration and validation processes followed using the SUFI-2 algorithm. For evaluating catchment simulation, two methods were used: i. model prediction uncertainty measured by P-factor and R-factor and ii. Model performance indicators, that is, Nash-Sutcliffe Efficiency (NSE), Coefficient of determination (R 2 ), Percent bias (PBIAS), and Residual variation (RSR). The P-factor achieved 0.77 and 0.68 while R-factor attained 1.31 and 1.82 for calibration and validation, respectively. The following indicators were used to evaluate the model performance through calibration and validation results respectively; NSE with 0.82 and 0.80, R 2 with 0.84 and 0.89, PBIAS achieving -20≤PBIAS≤-1.1 and RSR performing 0.42 and 0.44. All performance indices achieved very good ratings apart from PBIAS validation which rated as satisfactory. The semi-arid characteristics together with relatively flat terrain features justified the need for the evaluation of model performance using discharge data in our study region. SWAT demonstrated reasonable results in modelling semi-arid streamflow with high and low flows adequately captured. Consequently, this evaluation was necessary for further investigations into impacts of climate change on scarce water resources highlighting the challenges of SWAT model applications in our study area climatic regime and other similar regions globally for further model improvements.

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Klima und Gesellschaft

Springer eBooks, 2024

Schlüsselthemen des Klimawandels

Springer eBooks, 2024

Spatio-temporal snowmelt variability across the headwaters of the Southern Rocky Mountains

Frontiers of Earth Science, Mar 22, 2017

Understanding the rate of snowmelt helps inform how water stored as snow will transform into stre... more Understanding the rate of snowmelt helps inform how water stored as snow will transform into streamflow. Data from 87 snow telemetry (SNOTEL) stations across the Southern Rocky Mountains were used to estimate spatio-temporal melt factors. Decreases in snow water equivalent were correlated to temperature at these monitoring stations for eight half-month periods from early March through late June. Time explained 70% of the variance in the computed snow melt factors. A residual linear correlation model was used to explain subsequent spatial variability. Longitude, slope, and land cover type explained further variance. For evergreen trees, canopy density was relevant to find enhanced melt rates; while for all other land cover types, denoted as non-evergreen, lower melt rates were found at high elevation, high latitude and north facing slopes, denoting that in cold environments melting is less effective than in milder sites. A change in the temperature sensor about mid-way through the time series (1990 to 2013) created a discontinuity in the temperature dataset. An adjustment to the time series yield larger computed melt factors.

Zur Stellung der Kartographie in den Geowissenschaften

KN - Journal of cartography and geographic information, Sep 1, 2006

Die Kartographie erfreut sich zunehmender gesellschaftlicher und wissenschaftlicher Aufmerksamkei... more Die Kartographie erfreut sich zunehmender gesellschaftlicher und wissenschaftlicher Aufmerksamkeit. Die Geowissenschaft „Kartographie” ist in den letzten Jahren gesellschaftlich „sichtbarer” geworden. Digitale Karten, Navigationssysteme und Auskunftssysteme prägen unser Alltagsleben, stehen immer mehr Menschen zur Verfügung und bestimmen gleichzeitig die Entwicklung und Stellung dieser Wissenschaft im Kanon der Geowissenschaften. In Zeiten einer stärker bildhaften und räumlichen Wahrnehmung unserer Erde entwickelt sich die Kartographie zur Leitdisziplin raumbezogener Visualisierung und übernimmt als Schnittstellenwissenschaft eine vermittelnde Schlüsselstellung im Kontext der Geoinformatik.

Spectral signatures of cultivated crops for GIS-supported applications in precision farming

In this contribution the usefulness of spectral reflectance data of canopy cover for applications... more In this contribution the usefulness of spectral reflectance data of canopy cover for applications in site specific crop management (ssm) is investigated. Field spectrometry and high resolution airborne spectrometer data (HyMap®) of different test sites in northern and north eastern Germany are evaluated with primary regard to the biochemical constituents and other geo- and biophysical parameters relevant for the yield potential of winter wheat stands. The spatial patterns of the spectral features are compared with other site specific characteristics to determine the accuracy of the measurements and to evaluate the relationships between canopy status, soil status and topographic parameters. Spectral information and auxiliary data form thematic layers for the implementation in a geographic information system specified to model the status of agricultural plots. The resulting data could provide useful and reliable information for inventory management of crop production.

Integrated Universal Soil Loss Equation (USLE) and Geographical Information System (GIS) for Soil Erosion Measurement in basin of Asap river, Central Vietnam

EGUGA, Apr 1, 2017

The study was conducted in Asap river basin, A Luoi district, Thua Thien Hue Province, Vietnam, u... more The study was conducted in Asap river basin, A Luoi district, Thua Thien Hue Province, Vietnam, using the Universal Soil Loss Equation (USLE) and Geographical Information System (GIS) to determine the soil erosion status. The results show strong effect of the heavy rainfall and high slope on the erosion level in the research area. More than 40% of land area lost over 10 tons/ha/year. The natural forest land lost the most by averagely is 38.4 tons/ha/year, while the agricultural land showed less with 2.79 tons for paddy rice land use type and 7.58 tons for upland crops yearly. Comparison between some places of Vietnam and the Southeast Asia showed that soil erosion in watersheds of Asap is more serious. We have been proposed a recommendation on changing the classification system of land use type in Vietnam for more accurate in soil erosion measurement.

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Global health

The challenges mankind is facing in the next decades are manifold, encompassing world population ... more The challenges mankind is facing in the next decades are manifold, encompassing world population growth predicted to reach 9 billion by 2050, climate change with temperature increases and changes in precipitation patterns, and more extreme and unpredictable weather events, which occur with increasingly higher amplitudes and frequencies. Additionally, environmental degradation, in combination with inadequate political frameworks, further contribute to food insecurity, malnutrition, bad health and depletion of natural resources. Among the regions most affected by and most vulnerable to climate change is Sub-Saharan Africa, where variability in onset and extent of rainy seasons, and significant reductions in the length of growing periods forecasted by many of the Global Climate Models as well as steadily increasing desertification and land use and land cover change will have direct impact on agricultural production. Besides the effects of exploitation and further loss of natural resources, the direct drivers of agricultural change, the growing food demand and changes in consumption patterns, are enhanced by factors such as global energy shortage, which further aggravate the situation (IAASTD 2008). As a result, Africa's agriculture, particularly in arid and semi-arid areas, is facing increased abiotic and biotic stress with disease outbreaks and insect epidemics, leading to a decline in crop yields, a decrease in forest and cultivated area shares, and a reduc- Andrea Holzäpfel In the year 2000, political leaders from around the world gave the world's biggest promise -to achieve the Millennium Development Goals (MDGs). The MDGs are a global pledge to reduce extreme poverty and human deprivation by half until 2015 through collaborative multilateral action. The MDGs comprise 8 quantifiable goals of which MDG 4,5 and 6 are directly related to improving health outcomes (improving child and maternal health and combating HIV/AIDS). As we move towards the target date of 2015 the critical question needs to be asked whether the MDGs have been a successful approach and what can be learned from the past 10 years for the formulation of the Post-MDG agenda. Certainly, the MDGs have generated great commitments from governments, international organizations, civil society, and even the private sector (Manning 2010). They have focused attention on key dimensions of human development and progress has been made in many areas. The 2010 UN-MDG Summit however drew attention to the fact that progress towards MDG 5 -improving maternal health -has been unacceptably slow. Child mortality also still remains dramatically high with 9 million children dying each year before their fifth birthday . At the G8 summit in 2010 the support to significantly reduce maternal and child mortality was reaffirmed by announcing the G8-Muskoka Initiative. In the Global Health -A Challenge for Interdisciplinary Research 35 The Göttingen International health Network (GIHN) has set out to meet this challenge. The Network brings together scientists from disciplines ranging from life sciences to geosciences and economics. Together they design and implement projects aiming to improve maternal and child health. As the health of mothers and children is influenced by a wide range of factors such as the quality of nutrition and water, economic determinants, implications of climate change, social relations and spiritual wellbeing all partners of the network can contribute their expertise to joint projects. Furthermore, GIHN embraces the concept of fostering South-South partnership by bringing together scientists from Ghana, Tanzania and India in equal partnerships. The aims of the Göttingen International Health Network are thus not only in line with the MDG 4,5 but also MDG 8 that calls for global partnership. Its collaborative approach ensures a mutual learning experience and the expansion of knowledge of all partners.

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Distribution of snow depth variability

Frontiers of Earth Science, Jun 22, 2018

Snow depth is the easiest snowpack property to measure in the field and is used to estimate the d... more Snow depth is the easiest snowpack property to measure in the field and is used to estimate the distribution of snow for quantifying snow storage. Often the mean of three snow depth measurements is used to represent snow depth at a location. This location is used as a proxy for an area, typically a digital elevation model (DEM) or remotely sensed pixel. Here, 11, 17, or 21 snow depth measurements were used to represent the mean snow depth of a 30-m DEM pixel. Using the center snow depth measurement for each sampling set was not adequate to represent the pixel mean, and while the use of three snow depth measurements improved the estimate of mean, there is still large error for some pixels. These measurements were then used to determine the variability of snow depth across a pixel. Estimating variability from few points rather than all in a measurement was not sufficient. The sampling size was increased from one to the total per pixel (11, 17, or 21) to determine how many point samples were necessary to approximate the mean snow depth per pixel within five percent. Binary regression trees were constructed to determine which terrain and canopy variables dictated the spatial distribution of the snow depth, the standard deviation of snow depth, and the sample size to within 5% of the mean per pixel. One location was measured in two years just prior to peak accumulation, and it is shown that there was little to no inter-annual consistency in the mean or standard deviation.

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Comparison of satellite soil moisture products of Mongolia and their relation to grassland development. Oyudari Vova 12 , Martin Kappas 2 , Ammar Rafiei Emmam 2 ;National university of Mongolia, Space Science and Remote Sensing Laboratory 1 ; Cartography, GIS and Remote Sensing Department, Instit...

AGU Fall Meeting Abstracts, Dec 1, 2019

Correlation analysis between forest carbon stock and spectral vegetation indices in Xuan Lien Nature Reserve, Thanh Hoa, Viet Nam

EGU General Assembly Conference Abstracts, Apr 1, 2017

Eco-hydrological modeling in a tropical area of Vietnam using SWAT model

EGUGA, Apr 1, 2016

Multi-source image reconstruction: exploitation of EO-1/ALI in Landsat-7/ETM+ SLC-off gap filling

Proceedings of SPIE, Feb 14, 2008

The Landsat-7 Enhanced Thematic Mapper Plus (ETM+) is the sensor payload on the Landsat-7 satelli... more The Landsat-7 Enhanced Thematic Mapper Plus (ETM+) is the sensor payload on the Landsat-7 satellite imager (launched on April 15th, 1999) that is a derivative of the Landsat-4 and 5 Thematic Mapper (TM) land imager sensors. Scan Line Corrector (SLC) malfunctioning appeared onboard on May 31, 2003. The SLC-Off problem was caused by failure of the SLC which compensates for

Nationalatlas Bundesrepublik Deutschland

Spektrum, Akad. Verl. eBooks, 2003

Evaluation of MODIS land surface temperature products for daily air surface temperature estimation in northwest Vietnam

International Journal of Remote Sensing, Feb 18, 2019

Recently, the MODerate resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST... more Recently, the MODerate resolution Imaging Spectroradiometer (MODIS) land surface temperature (LST) is considered one of the most suitable ways to retrieve air surface temperature (T a )one of the most important and widely used climate variables for a wide range of applications. In fact, many successful studies have been reported in many regions of the world. Each day, four MODIS LST data are available; from two sensors (Terra and Aqua) at two local overpass times (daytime and night-time). However, due to their different overpass times, most studies have used LST daytime and night-time for daily maximum (T max ) and minimum (T min ) air surface temperature estimation, respectively. Therefore, the performance of each individual LST data, the effect of the dynamic combination of these four LST data, the effect of land surface characteristics, and the effect of LST quality on the same estimation in the same region on the accuracy of estimated T a remains unclear. In this study, we evaluated and tested all individual LST data as well as all possible combinations of the four MODIS LST data from two separate stations with distinct land surface characteristics in northwest Vietnam for 10 years (from 2004 to 2013) under two sky conditions (all clear sky conditions and only good datai.e. Quality Control (QC) value of 0) for daily T a (T max , T min , and T mean ) estimations. In addition, the mixed data of the two stations were also evaluated. Our results showed that Terra LST data have a higher correlation with T a than Aqua LST; which is consistent for both stations and both quality conditions (all clear sky and only good data). A closer overpass time with T max or T min occurrence time did not guarantee a higher accuracy of T a estimation. Using only good LST data produced a higher accuracy of T a estimation than using all clear sky data. However, if the percentage of good data is low (i.e. less than 30%), then the all clear sky data will provide better results for T max estimation. Comparing the performance of the different combinations when using the single station and mixed station data, combinations including at least one nighttime LST produced stable and high accuracy T min and T mean estimates, while the combinations with only daytime LST produced very low accuracy results. For T max estimation, the results were less impacted by LST quality; however, they were strongly impacted by different combinations and land surface characteristics.

format_quoteConoi station showed 67.5% good quality clear sky data, enhancing T a estimation consistency over Muongte's 25.7%.format_quote

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BioSTAR, a New Biomass and Yield Modeling Software

AGU Fall Meeting Abstracts, Dec 1, 2013

Comparison of the New LEAF Area INDEX (LAI 3G) with the Kazahstan-Wide LEAF Area INDEX DATA SET (GGRS-LAI) over Central ASIA

AGU Fall Meeting Abstracts, Dec 17, 2014

Integrated Landscape Evaluation. Using Digital Aerial Photo Analysis and a Grid-Based Geographic Analysis System

Towards precision forestry: Drought response from remote sensing-based disturbance monitoring and fine-scale soil information in Central Europe

Science of The Total Environment, Jul 1, 2023

An evaluation of the Land Cover Classification Product Sentinel 2 Prototype Land Cover 20 m Map of Africa 2016 for Namibia

Global information on land cover is a primary output of remote sensing applications due to its im... more Global information on land cover is a primary output of remote sensing applications due to its importance to global change sciences, but also to governments and international initiatives. Consequently, a variety of land cover datasets have been developed in the past. Today users can choose among different products with various spatial resolutions for applications on global as well as on regional scales. A new classification covering the African continent was released by the European Space Agency only recently. Thanks to its mapping approach of 20 m, the Sentinel 2 Prototype Land Cover 20 m Map of Africa 2016 constitutes a novelty among the freely available products. However, being only a prototype, it is still missing final validation. This study aimed at evaluating the classification for the extent of Namibia by quantitatively and qualitatively comparing it to a selection of four low- to medium-resolution land cover products. Within the framework of an accuracy assessment for four test sites, statistical parameters were calculated which served as indicators for assessing the classification quality. According to the analysis, the overall accuracy of the prototype land cover product is on a medium level attaining approximately 54%. The per class accuracy varies from 2% to 100% suggesting that some classes require considerable reworking whereas others need less improvement. However, compared to the reference datasets, the prototype classification already constitutes a major development in land cover mapping.

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