Assessment of minimum vital flow in impacted lotic
environments
The minimum vital flow (MVF) is a management tool of particular interest designed to cope with critical situations that arise in river ecosystems due to large exploitation of natural discharge for civil, industrial or agricultural purposes. Until now the application of the MVF is limited to the assessment of the minimum hydrological component for the survival of biological communities, while it appears more and more important to move to an integrated assessment of ecological and economic aspects aiming at the preservation of the river ecosystem and its functions. Indeed, at the European level is open a discussion on the definition of the environmental flow (EF), which is the quantity, quality and timing of water flow required to sustain ecosystems and the services they provide. The EF is also connected with the objectives of the WFD (2000/60/EC) and then with the achievement of good ecological status for all water bodies (Sánchez Navarro & Schmidt, 2012).
In this context the Laboratory of Aquatic Ecology started to study the Oglio and Mincio river ecosystems (Po valley, northern Italy) with a site-specific experimental project (up to 6 years) to define the MVF. These two rivers are characterized by numerous dams or weirs and withdrawals or abstractions for irrigation purposes and for hydroelectric power generation. The responses of physico-chemical parameters and biological communities (macrophytes, macroinvertebrates and diatoms) were investigated on a seasonal basis in relation to different discharge scenarios (base flow: 5% of the mean annual flow; different scenario from 5 to 15% were tested on a weekly or monthly base).
After the first three years, the collected physico-chemical data were integrated to calculate the LIMeco index (based on: dissolved oxygen, nitrate, ammonia and total phosphorous), and correlation with discharge data was tested. Any significant relationship was not found, because the value of the quality index is determined by nitrate concentration which is the main pollutant in the Po River plain. In the Oglio River multivariate analyses of physico-chemical parameters and discharge data collected in summer (maximum water abstraction) highlighted the role of diffusive nutrient sources and hydrology in identifing three different river reaches. The water chemistry of the first segment is characterized by the Iseo Lake water, the second one is fed by groundwaters, and the last one by the secondary canal network which drains intensive agricultural land.
The results of biological communities are reported in the page here.
From this first experience arise that the indicators used are not suitable for the MVF definition. In the next three years of the Oglio River project, the use of the experimental sampling will be based on discharge scenario more longer (seasonal duration) than that tested until now. Moreover, the interaction between river and groundwater will be investigate by means of conservative parameters (chloride or sulfate) together with nitrate, following diel and seasonal hydrology. The physico-chemical and discharge data will be analyzed evaluating their spatial and temporal auto-correlation.
In this context the Laboratory of Aquatic Ecology started to study the Oglio and Mincio river ecosystems (Po valley, northern Italy) with a site-specific experimental project (up to 6 years) to define the MVF. These two rivers are characterized by numerous dams or weirs and withdrawals or abstractions for irrigation purposes and for hydroelectric power generation. The responses of physico-chemical parameters and biological communities (macrophytes, macroinvertebrates and diatoms) were investigated on a seasonal basis in relation to different discharge scenarios (base flow: 5% of the mean annual flow; different scenario from 5 to 15% were tested on a weekly or monthly base).
After the first three years, the collected physico-chemical data were integrated to calculate the LIMeco index (based on: dissolved oxygen, nitrate, ammonia and total phosphorous), and correlation with discharge data was tested. Any significant relationship was not found, because the value of the quality index is determined by nitrate concentration which is the main pollutant in the Po River plain. In the Oglio River multivariate analyses of physico-chemical parameters and discharge data collected in summer (maximum water abstraction) highlighted the role of diffusive nutrient sources and hydrology in identifing three different river reaches. The water chemistry of the first segment is characterized by the Iseo Lake water, the second one is fed by groundwaters, and the last one by the secondary canal network which drains intensive agricultural land.
The results of biological communities are reported in the page here.
From this first experience arise that the indicators used are not suitable for the MVF definition. In the next three years of the Oglio River project, the use of the experimental sampling will be based on discharge scenario more longer (seasonal duration) than that tested until now. Moreover, the interaction between river and groundwater will be investigate by means of conservative parameters (chloride or sulfate) together with nitrate, following diel and seasonal hydrology. The physico-chemical and discharge data will be analyzed evaluating their spatial and temporal auto-correlation.
References:
Guareschi S., Laini A., Racchetti E., Bo T., Fenoglio S., Bartoli M., 2014. How do hydromorphological constraints and regulated flows govern macroinvertebrate communities along an entire lowland river? Ecohydrology, 7(2): 366-377.
Bolpagni R., Laini A., Racchetti E., Bartoli M., Viaroli P., 2012. Analisi delle comunità a macrofite del fiume Oglio sublacuale: prime evidenze per una loro valutazione eco-funzionale. Biologia Ambientale, 26: 29-37.
Guareschi S., Laini A., Racchetti E., Bo T., Fenoglio S., Bartoli M., 2014. How do hydromorphological constraints and regulated flows govern macroinvertebrate communities along an entire lowland river? Ecohydrology, 7(2): 366-377.
Bolpagni R., Laini A., Racchetti E., Bartoli M., Viaroli P., 2012. Analisi delle comunità a macrofite del fiume Oglio sublacuale: prime evidenze per una loro valutazione eco-funzionale. Biologia Ambientale, 26: 29-37.