Arid regions, that have a terrestrial share of 30 %, heavily rely on groundwater for do-mestic, industrial and irrigation purposes. The reliance on groundwater has partly turned into a dependency in areas where the increasing population number and the expansion of irrigated agricultural areas demand more groundwater than is naturally replenished. Yet, spatial and temporal information on groundwater are often scarce induced by the facts that groundwater is given a low priority in many national budgets and numerous (semi-) arid regions in the world encompass large and inaccessible areas. Hence, there is an urgent need to provide low-cost alternatives that in parallel cover large spatial and temporal scales to gain information on the groundwater system.
Remote sensing holds a tremendous potential to represent this alternative. The main objective of this thesis is the improvement of existing and the development of novel remote sensing applications to infer information on the scarce but indispensable resource groundwater at the example of the Dead Sea. The background of these de-velopments relies mainly on freely available satellite data sets. I investigate 1) the pos-sibility to infer potential groundwater flow-paths from digital elevation models, 2) the applicability of multi-temporal thermal satellite data to identify groundwater discharge locations, 3) the suitability of multi-temporal thermal satellite data to derive information on the long-term groundwater discharge behaviour, and 4) the differences of thermal data in terms of groundwater discharge between coarse-scaled satellite data and fine-scaled airborne data including a discharge quantification approach.
1) I develop a transparent, reproducible and objective semi-automatic approach us-ing a combined linear filtering and object based classification approach that bases on a medium resolution (30 m ground sampling distance) digital elevation model to extract lineaments. I demonstrate that the obtained lineaments have both, a hydrogeological and groundwater significance, that allow the derivation of potential groundwater flow-paths. These flow-paths match results of existing groundwater flow models remarkably well that validate the findings and shows the possibility to infer potential groundwater flow-paths from remote sensing data.
2) Thermal satellite data enable to identify groundwater discharge into open water bodies given a temperature contrast between groundwater and water body. Integrating a series of thermal data from different periods into a multi-temporal analysis accounts for the groundwater discharge intermittency and hence allows obtaining a representa-tive discharge picture. I analyse the constraints that arise with the multi-temporal anal-ysis (2000-2002) and show that ephemeral surface-runoff causes similar thermal anomalies as groundwater. To exclude surface-runoff influenced data I develop an au-tonomously operating method that facilitates the identification. I calculate on the re-maining surface-runoff uninfluenced data series different statistical measures on a per pixel basis to amplify groundwater discharge induced thermal anomalies. The results reveal that the range and standard deviation of the data series perform best in terms of anomaly amplification and spatial correspondence to in-situ determined spring dis-charge locations. I conclude on the reason that both mirror temperature variability that is stabilized and therefore smaller at areas where spatio-temporal constant groundwater discharge occurs.
3) The application of the before developed method on a thermal satellite data set spanning the years 2000 to 2011 enables to localise specific groundwater discharge sites and to semi-quantitatively analyse the temporal variability of the thermal anomalies (termed groundwater affected area - GAA). I identify 37 groundwater discharge sites along the entire Dead Sea coastline that refine the so far coarsely given spring areas to specific locations. All spatially match independent in-situ groundwater discharge observations and additionally indicate 15 so far unreported discharge sites. Comparing the variability of the GAA extents over time to recharge behaviour reveals analogous curve progressions with a time-shift of two years. This observation suggests that the thermally identified GAAs directly display the before only assumed groundwater discharge volume. This finding provides a serious alternative to monitor groundwater discharge over large temporal and spatial scales that is relevant for different scientific communities. From the results I furthermore conclude to observe the before only assumed and modelled groundwater discharge share from flushing of old brines during periods with an above average Dead Sea level drop. This observation implies the need to not only consider discharge from known terrestrial and submarine springs, but also from flushing of old-brines in order to calculate the total Dead Sea water budget.
4) I present a complementary airborne thermal data set recorded in 01/2011 over the north-western part of the Dead Sea coast. The higher spatial resolution allows to refine the satellite-based GAA to 72 specific groundwater discharge sites and even to specify the so far unknown abundance of submarine springs to six sites with a share of <10 % to the total groundwater discharge. A larger contribution stems from newly iden-tified seeping spring type (24 sites) where groundwater emerges diffusively either ter-restrial or submarine close to the land/water interface with a higher share to the total discharge than submarine springs provide. The major groundwater contribution origi-nates from the 42 identified terrestrial springs. For this spring type, I demonstrate that 93 % of the discharge volume can be modelled with a linear ordinary least square re-gression (R2=0.88) based on the thermal plume extents and in-situ measured discharge volumes from the Israel Hydrological Service. This result implies the possibility to determine discharge volumes at unmonitored sites along the Dead Sea coast as well that can provide a complete physically-based picture of groundwater discharge magni-tude to the Dead Sea for the first time.
| Identifer | oai:union.ndltd.org:DRESDEN/oai:qucosa.de:bsz:105-qucosa-122757 |
| Date | 11 October 2013 |
| Creators | Mallast, Ulf |
| Contributors | TU Bergakademie Freibgerg, Geowissenschaften, Geotechnik, Bergbau, Helmholtz Centre for Environmental Research - UFZ, Dept. Catchment Hydrology, Dr. Richard Gloaguen, Dr. Christian Siebert, Prof. Martin Sauter, Dr. Richard Gloaguen, Dr. Stefan Geyer, Prof. Dr. Okke Batelaan, Dr. Christian Siebert |
| Publisher | Technische Universitaet Bergakademie Freiberg Universitaetsbibliothek "Georgius Agricola" |
| Source Sets | Hochschulschriftenserver (HSSS) der SLUB Dresden |
| Language | English |
| Detected Language | English |
| Type | doc-type:doctoralThesis |
| Format | application/pdf |
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