INTRODUCTION

Wetlands are linking terrestrial and aquatic ecosystems, therefore they are of great value and play a significant role in the natural environment. Wetlands are the source of sweet water and act as filters between upstream and rivers estuaries  They are also characterized by high biodiversity and for being an important part of animal migration routes . Often, due to very high biomass production, wetlands are also responsible for recycling and storing large amount of methane, nitrogen, phosphorus, biogenic silica and carbon. Wetland ecosystems are very sensitive to changes in water quantity and quality and their functioning can be easily affected. Wetlands ecosystems are highly variable and depending on their surface- and groundwater relations developing a working hydrological model is a very complex task especially if some additional conditions are included e.g. flooding. Due to the high importance and vulnerability of wetland ecosystems there is a need for developing proper tools to maintain a good quality of those areas. Proper monitoring of changes in often very vast and hard to access area is not an easy task and requires more improved and complex tools. 

OBJECTIVES

The HiWET project aims at developing a tool for efficient freshwater wetland ecosystem monitoring and evaluation of ecosystem health, using novel techniques to estimate evapotranspiration (ET) and to derive evaporative stress as an indicator for the health state of the wetland vegetation. The project targets consistent ET retrieval across scales, from the local field scale (fine resolution) to the regional catchment scale (coarse resolution) derived from combined use of hydrological models and remote sensed energy balances. In addition the project aims to contribute greatly to an increased understanding of the functioning of freshwater wetland ecosystems.

METHODOLOGY

Plants are showing different temperature according to their water content. Dry vegetation is more warm (left plant in the picture) than one with sufficient amount of water (right plant).

Plants are showing different temperature according to their water content. Dry vegetation is more warm (left plant in the picture) than one with sufficient amount of water (right plant).

The Project has many objectives however one of the most important is to provide a tool that would allow an easy access to a thematic map with various data. These maps will show spatial or temporal distribution of many parameters however the most relevant element is to provide maps for monitoring wetland health status by associating changes in freshwater with ecosystem functioning. Users have different background and expectations therefore final product will allow to display a selection of information that will be both useful and interesting for farmers, land managers, tourists, ecologists or scientists depending on their needs.

Image of Doode Bemde acquired during a flight campaign. Thermal image (below) is showing a high spatial variability of temperature according to the land use e.g. forests, fields, grasslands.

Image of Doode Bemde acquired during a flight campaign. Thermal image (below) is showing a high spatial variability of temperature according to the land use e.g. forests, fields, grasslands.

Energy or hydrological models are a simplified presentation of processes existing in the nature. However models in their predictions are suppose to be as accurate as possible therefore there is a need for making a comparison between their results and real data collected in a field.Complex model in its predictions also need to take many elements in consideration e.g. plants properties. Proper parametrization of vegetation can only be done based on collected in the field data.  Therefore all efforts with developing a model are also associated with many field campaigns in which various advanced equipment is involved. Data collected in a field (ground truth data) is also used for making a comparison with images taken by satellites to make sure if everything is correct. As it is shown in the picture collected data can be (from left to right) related to spectral measurements (interaction between matter and electromagnetic radiation), GPS coordinates (for matching field measurements with remote sensing images), LAI - leaf area index (how much surface is covered by leaves), remote sensing images, thermal images or drones.

However to achieve this goal much work must be done in data collecting, processing and developing a software that will provide information about the health status of environment. The main idea is based on high temperature spatial variability in ecosystem due to non equal water distribution. New thematic map will come as a result of modelling that would be based on water and energy balance approach that assumes constant circulation of water and energy in an environment between various elements like soil, water bodies, vegetation and atmosphere. Designing and integrating model with dynamic data is an innovative approach that would allow monitoring wetland health status and evapotranspiration. Evapotranspiration is a sum up of two processes – evaporation and transpiration (plants respiration function) and is strongly related to the temperature. Plants that suffers from insufficient amount of water (water stress) have higher temperature which can be tracked with thermal cameras.  Images that are shown below were taken from a plane and are an example of an input data that can be used for modelling.

As data collection and building a detailed meteo- hydro- and ecological database is the first big step than another one is processing data and building a model. Models work like a software that from input data are calculating and predicting various values. Most hydrological models were, however developed in the early 90s and in order to compute the hydrological mass balance they used conservation of mass principle (constant flow of water) without considering the energy balance. Compared to modern knowledge and technology traditional models are mostly limited because they simplify some hydrological processes or do not even include wetland areas in calculations. Also in that time remote sensing was a very expensive technology under intense development. Images from satellites are nowadays taken more often and are more accessible therefore it is much easier to monitor vast areas. The HiWET project will focus on developing software that would find a way of using a more dynamic remotely sensed data for distant and hardly accessible areas like wetlands.