Periodic Reporting for period 2 - OPTWET (Finding optimal size and location for wetland restoration sites for best nutrient removal performance using spatial analysis and modelling)
Período documentado: 2017-04-01 hasta 2018-03-31
A growing economy and population in the world is causing large-scale land use and landscape changes and an increasing pressure is put on water resources all over the world. Diffuse water pollution that is mainly driven by agricultural food production, is considered to be one of the major problems for water quality in many countries. Wetlands play a key role in controlling flooding and diffuse source pollution. Most of the former wetland area in many areas of the world has been lost due to draining for agricultural production, and the trend is continuing particularly for small wetlands in agricultural landscapes. There is a need for detailed identification and assessment of the wetlands remaining, and also of potential locations for wetland rehabilitation and creation to help manage diffuse contaminant losses that originate from continuously intensifying agriculture.
The main prerequisite for combating excessive nutrient losses to water bodies is to study how the pollution sources can be traced and reduced. Compared to point pollution, diffuse water pollution is more complex and difficult to control due to its numerous and dispersed sources, and the difficulties in tracing its pathways. This project aims to identify how effective are wetlands in removing nutrients and what is the optimal land use in agricultural catchments to reduce nutrient (nitrogen and phosphorus) loads in catchments.
The main prerequisite for combating excessive nutrient losses to water bodies is to study how the pollution sources can be traced and reduced. Compared to point pollution, diffuse water pollution is more complex and difficult to control due to its numerous and dispersed sources, and the difficulties in tracing its pathways. This project aims to identify how effective are wetlands in removing nutrients and what is the optimal land use in agricultural catchments to reduce nutrient (nitrogen and phosphorus) loads in catchments.
Fusion of high resolution orthophotos (0.4 m), Landsat imagery (30 m) and LiDAR based terrain indices (Topographic Wetness Index) were used to identify small-scale wetlands in the Waituna catchment in the Southland region, New Zealand. Suitability modelling approach was used to identify the spatial distribution of the sites most suited to wetland creation or restoration. We calculated the area, average depth, and water storage capacity for each modelled wetland based on the flooded area. The study showed that terrain analysis using high-resolution topographical data can produce suitability maps for wetlands that can be easily used by decision makers and planners in watershed management. The rapid methodology reveals potential wetland creation or restoration sites at a reasonable cost; with the resulting spatially explicit suitability map, managers can plan for wetland creation or restoration without having to wait for field-data collection.
On a the wetland level, a simple dynamic model operating on an hourly time step was used to explore potential wetland nitrogen removal performance of a wetland in Waikato region, New Zealand. Hourly measurements of inflow, outflow, rainfall and Penman evapotranspiration estimates were used to calculate a dynamic water balance for the wetland. In addition, nitrogen concentration measurements at inflow, outflow and piezometers installed in the wetland were used as input data for the model. A dynamic nitrogen-N mass balance was calculated by coupling influent concentrations to the dynamic water balance and applying a first order areal removal coefficient (k20) adjusted to the ambient temperature. Storm events above a certain threshold were assumed to always result in surface runoff or overland flow and were assigned higher nitrate based on surface run-off measurements. The removal efficiency was estimated for all nitrogen forms.
On catchment level, nitrogen and phosphorus losses were modelled 28-year period in the Porijõgi catchment, Estonia. An empirical model was used to model nutrient losses. Land use pattern, soil information, fertilization factor and hydrology factors were used as inputs for the model.The N and P runoffs declined following the post-Soviet collapse of agriculture, and stabilised at low output during the 1990s and early 2000s. Introduction of the European Union Common Agricultural Policy (CAP) reintensified the agriculture and somewhat rebounded the N and P discharges.
For spatial planning and implementation suitability modelling approach was used on spatial data to create a methodology for national-scale determination of Estonia’s green infrastructure and conflict hotspots between green infrastructure and human influenced areas to indicate the need for ecological engineering measures like the construction of buffer ecosystems, such as wetlands that are capable of capturing and treating wastewater, agricultural runoff, and stormwater.
Altogehter one book chapter and eight scientific papers in peer-reviewed journals were published. The results of this research have been presented in several local ( NZ Hydrological Society Conference and NZ Ecological Society Conference, Annual Conference of Estonian Geoinfinformatics Society) and international conferences (for example EGU and Ecosummit).
Two meetings with DairyNZ focusing on collaboration in modelling nutrient runoff and also possible use of current work on identifying wetlands using remote sensing in a practical tool for farmers. Several press releases and social media posts were made about the project progress and outcomes.
On a the wetland level, a simple dynamic model operating on an hourly time step was used to explore potential wetland nitrogen removal performance of a wetland in Waikato region, New Zealand. Hourly measurements of inflow, outflow, rainfall and Penman evapotranspiration estimates were used to calculate a dynamic water balance for the wetland. In addition, nitrogen concentration measurements at inflow, outflow and piezometers installed in the wetland were used as input data for the model. A dynamic nitrogen-N mass balance was calculated by coupling influent concentrations to the dynamic water balance and applying a first order areal removal coefficient (k20) adjusted to the ambient temperature. Storm events above a certain threshold were assumed to always result in surface runoff or overland flow and were assigned higher nitrate based on surface run-off measurements. The removal efficiency was estimated for all nitrogen forms.
On catchment level, nitrogen and phosphorus losses were modelled 28-year period in the Porijõgi catchment, Estonia. An empirical model was used to model nutrient losses. Land use pattern, soil information, fertilization factor and hydrology factors were used as inputs for the model.The N and P runoffs declined following the post-Soviet collapse of agriculture, and stabilised at low output during the 1990s and early 2000s. Introduction of the European Union Common Agricultural Policy (CAP) reintensified the agriculture and somewhat rebounded the N and P discharges.
For spatial planning and implementation suitability modelling approach was used on spatial data to create a methodology for national-scale determination of Estonia’s green infrastructure and conflict hotspots between green infrastructure and human influenced areas to indicate the need for ecological engineering measures like the construction of buffer ecosystems, such as wetlands that are capable of capturing and treating wastewater, agricultural runoff, and stormwater.
Altogehter one book chapter and eight scientific papers in peer-reviewed journals were published. The results of this research have been presented in several local ( NZ Hydrological Society Conference and NZ Ecological Society Conference, Annual Conference of Estonian Geoinfinformatics Society) and international conferences (for example EGU and Ecosummit).
Two meetings with DairyNZ focusing on collaboration in modelling nutrient runoff and also possible use of current work on identifying wetlands using remote sensing in a practical tool for farmers. Several press releases and social media posts were made about the project progress and outcomes.
Agricultural pollution loads are increasing all over the world and there is need to find most effective ways to reduce those loads but at the same time retain the agricultural production. Wetlands are one of the most effective practices that can remove nutrients from surface waters. Due to intensifying agriculture, wetlands have been drained and converted for centuries all around the world. The remaining wetlands are fragmented and often in a degraded state. Ground-based surveys of small wetlands are time consuming and analysis of aerial photographs and satellite images is affected by trees. The use of terrain analysis to predict “potential” wetlands has the advantage of being systematic and avoids problems caused by trees. New monitoring techniques with high temporal and spatial resolution offer improved opportunities to analyse flow paths and determine suitable locations for wetland restoration.
The developed method for identifying existing wetlands and wetland restoration sites helps to speed up finding and pre-processing the input data needed for catchment management. The method can be used either at farm-scale or at a catchment scale to identify wetland restoration sites which is a pre-condition for modelling their effectiveness in nutrient removal. As it is using remote sensing data it is possible to use always up-to-date input which is an important aspect in the quickly changing world.
For estimating the removal efficiency of wetlands, a model was developed that helps to assess nutrient removal performance of wetlands and is designed to be potentially used for any wetland. Estimating wetland nutrient removal efficiency also enables to evaluate their cost-effectiveness which is an important factor for planning their restoration.
The study also helps to raise awareness of the functions and values of wetlands in the eyes of the farmers and in the eyes of the society in general. As wetlands’ nutrient removal efficiency per unit land area can be very high, farmers might be incentivised to not drain these natural wetlands and fence them off to prevent stock access in order to maintain their nutrient removal functions.
The developed method for identifying existing wetlands and wetland restoration sites helps to speed up finding and pre-processing the input data needed for catchment management. The method can be used either at farm-scale or at a catchment scale to identify wetland restoration sites which is a pre-condition for modelling their effectiveness in nutrient removal. As it is using remote sensing data it is possible to use always up-to-date input which is an important aspect in the quickly changing world.
For estimating the removal efficiency of wetlands, a model was developed that helps to assess nutrient removal performance of wetlands and is designed to be potentially used for any wetland. Estimating wetland nutrient removal efficiency also enables to evaluate their cost-effectiveness which is an important factor for planning their restoration.
The study also helps to raise awareness of the functions and values of wetlands in the eyes of the farmers and in the eyes of the society in general. As wetlands’ nutrient removal efficiency per unit land area can be very high, farmers might be incentivised to not drain these natural wetlands and fence them off to prevent stock access in order to maintain their nutrient removal functions.