Evaluating various geoinformatic methods of assessing access to water by using Open Data : Case study: Nam Ngum
Segessenmann, Frank (2017)
Metropolia Ammattikorkeakoulu
2017
Creative Commons Attribution-NonCommercial-ShareAlike 1.0 Finland
Julkaisun pysyvä osoite on
https://urn.fi/URN:NBN:fi:amk-2017053111387
https://urn.fi/URN:NBN:fi:amk-2017053111387
Tiivistelmä
This thesis document contains a review of the major researches on different water indicators and indexes.The research on the subject first started in the mid-seventies, and the results are still valuable. The study chosen to be replicated was the Spatial unit non-overlapping WSI model (Sun-WSI) which use the resources found in the surrounding area of an active cell to calculate water stress. The Sun-WSI area defining the surroundings is a circle. Marko Kallio proposed to implement GIS distance analysis methods by using a village point to simulate the access available to water.
One of the biggest difficulties in replicating the methods was the hydrological modelling software. It was not possible to use the same software as in the Sun-WSI study. Marko Kallio had worked for his Bachelor thesis and for other projects in the area of Nam Ngum. He provided the hydrological modelling software from a Finnish company. The main benefit was the access to the output and input time series in the area of the Nam Ngum catchment. The IWRM model generated the discharge layer for the dry and wet season.
The next step was to implement the distance analysis methods. In order to create the surface cost layer, it was necessary to find the appropriate factors to define the cost. In this study slope steepness, road networks and land use was used emphasizing the access from any village. An accumulation layer was necessary in order to create an irregular shape around the starting point, and the starting point, a cost surface layer and a threshold was required to generate the accumulation cost.
Finally, by using Matlab, different algorithms were created to compensate for some limitations found along the way. As much as possible from the Sun-WSI was replicated, but most of its sophisticated techniques were not possible to put in place. On the other hand, the idea proposed by Marko Kallio was met with success. The Village’s Accumulation Cost Area (VACA) was generated for each of the villages. The threshold and the accumulation cost layer were generated explicitly for each village. As expected, the water stress was reduced after the resource available inside the VACA was taken into account in the calculation.
One of the biggest difficulties in replicating the methods was the hydrological modelling software. It was not possible to use the same software as in the Sun-WSI study. Marko Kallio had worked for his Bachelor thesis and for other projects in the area of Nam Ngum. He provided the hydrological modelling software from a Finnish company. The main benefit was the access to the output and input time series in the area of the Nam Ngum catchment. The IWRM model generated the discharge layer for the dry and wet season.
The next step was to implement the distance analysis methods. In order to create the surface cost layer, it was necessary to find the appropriate factors to define the cost. In this study slope steepness, road networks and land use was used emphasizing the access from any village. An accumulation layer was necessary in order to create an irregular shape around the starting point, and the starting point, a cost surface layer and a threshold was required to generate the accumulation cost.
Finally, by using Matlab, different algorithms were created to compensate for some limitations found along the way. As much as possible from the Sun-WSI was replicated, but most of its sophisticated techniques were not possible to put in place. On the other hand, the idea proposed by Marko Kallio was met with success. The Village’s Accumulation Cost Area (VACA) was generated for each of the villages. The threshold and the accumulation cost layer were generated explicitly for each village. As expected, the water stress was reduced after the resource available inside the VACA was taken into account in the calculation.