Meet Petite Glâne – Swiss Case Study

The Petite Glâne catchment, located in the western Swiss Plateau within the Cantons of Fribourg and Vaud, is one of the OPTAIN project case studies. This region is characterized by its diverse agricultural activities and unique environmental challenges, making it an ideal case study for implementing and assessing Natural/Small Water Retention Measures (NSWRMs).

Background 

The Swiss Case Study focuses on the Petite Glâne catchment, an area known for being highly suitable for arable farming: nearly three quarters of its area consists of pastures and cropland. The upper zone of the catchment has rolling hills, and the Petite Glâne stream remained semi-natural and lined with forest. In contrast, the lower part of the catchment is part of the Broye plain, which is flat, with intensive agriculture, and a channelized and straightened stream. 

The primary agricultural activities in this region include crop cultivation and livestock farming. Farmers are growing various crops suited to the temperate climate such as corn, wheat, rapeseed, sugar beet and potatoes.  

Environmental challenges

Although the soil and climate are highly suitable for arable farming, the region is increasingly experiencing water shortages during summer. There is often not enough water in the Petite Glâne and the bigger Broye river for irrigation. In addition, extreme events with heavy rainfall are increasing in frequency and intensity. These challenges impact both the environment and agricultural productivity and will further aggravate with climate change. 

These changes pose significant risks to the sustainability of agricultural practices in the region. Against this background, OPTAIN explores efficient land use and land management strategies as well as technical measures that increase the capacity of soils to absorb and store water while improving nutrient retention and decomposition. These natural and small water retention measures (NSWRMs) are discussed and evaluated jointly with a Multi-Actor Reference Group (MARG).

Figure 1: Water retention problems in the Petite Glâne catchment: waterlogging in 2021 (left) and dry period in 2022 (right)

Stakeholder Engagement

Figure 2: Workshops with local stakeholders in 2021 (left) and 2022 (right) in Avenches, Switzerland. 

Active involvement of the MARG with local stakeholders is a cornerstone of the OPTAIN project in the Petite Glâne catchment. Farmers, authorities from the agricultural and environmental sector, environmental organizations, and researchers are integrated into the decision-making process. The project also collaborates with the Centre for Agricultural Advisory and Extension Services, AGRIDEA, to enhance stakeholder engagement and knowledge transfer

NSWRMs

As in all 14 OPTAIN case studies, in the Swiss case study, the project employs a harmonized approach to select, document and model Natural Small Water Retention Measures (NSWRM) including the MARG.

• Identification of NSWRMA standardized questionnaire was developed to gather data on existing and potential NSWRM. The questionnaire covered aspects such as land use type, implementation status, socio-economic and ecological impacts, and feasibility.

• Prioritization of MeasuresThrough a MARG workshop, stakeholders reviewed and prioritized measures based on local relevance, feasibility, and potential benefits.
• Selection of MeasuresFrom the prioritized list, five NSWRM have been selected to for further documentation and modelling. Selection criteria included relevance, representability in OPTAIN models, and availability of expertise.
• Documentation of MeasuresSelected measures (see below) have been documented in more detail using the WOCAT Global SLM database (www.wocat.net), ensuring standardization and accessibility. Through this documentation, the NSWRM will also feed into the NWRM.eu platform and the OPTAIN Learning Environment, which is currently being finalized.
• Integration into the Soil and Water Assessment Tool (SWAT)The selected NSWRM have been incorporated into the SWAT model, which was previously calibrated and validated against crop yield and discharge at the catchment outlet to ensure reliability. Initial simulation results have been generated and discussed with national experts to verify the plausibility of the outcomes and refine further analyses.

First results indicate that the measures impact both water quantity as well as quality. For the water balance, the NSWRM low tillage combined with cover crops has the most significant impact: it retains the water in the catchment area, reducing the maximum stream flow and increasing percolation and soil water. Low-tillage with cover crops also significantly reduces the average sediment loss from the agricultural fields. Similarly, though at a lesser extent, the NSWRM slope subdivision with grass seam also shows high potential in reducing sediment loss. Furthermore, riparian buffers are crucial in holding back sediments and nutrients, thereby reducing sediment and nutrient loads in water.

Figure 3: First results of modeling the impacts of selected NSWRMs on water balance as well as nutrients and sediments.

• Modelling of various scenarios and optimal NSWRM allocationTo assess the effectiveness of NSWRM under different conditions, various scenarios have been simulated, evaluating the impact of different NSWRM combinations while considering environmental and socio-economic indicators. The possible allocation and limitations of NSWRM in the Swiss case studies were previously discussed with MARG to ensure the plausibility of results. The optimization is currently being finalized and will be further reviewed in a MARG workshop scheduled for April 2025, organized jointly with AGRIDEA.

For Petite Glâne, this structured approach ensures that the following selected NSWRM are locally relevant, well-documented, and integrated into broader water retention strategies within the OPTAIN framework.

Conclusions

The efforts in the Petite Glâne catchment underscore the significance of integrating agricultural practices with environmental conservation through the implementation of NSWRMs. By addressing nutrient runoff and preparing for climate change impacts, these measures aim to enhance water quality, support biodiversity, and promote sustainable agriculture. The collaborative approach adopted in this case study serves as a model for similar initiatives in other regions, highlighting the importance of stakeholder engagement and tailored solutions in achieving environmental and agricultural sustainability.

Authors: Joana Eichenberger and Tatenda Lemann