Persist or perish: critical life stages determine the sensitivity of invertebrates to disturbances
Lee, Gea H. van der; Kraak, Michiel H.S. ; Verdonschot, Ralf C.M. ; Verdonschot, Piet F.M. - \ 2020
Aquatic Sciences 82 (2020)2. - ISSN 1015-1621
Agapetus fuscipes - Bioassessment - Discharge - Life cycle - Lowland streams
A large proportion of studies assessing the impact of disturbances on the invertebrate community composition focus on a single life stage, assuming that those are an adequate indicator of environmental conditions. The effect of a specific disturbance may, however, depend on the life stage of the exposed organism. Therefore, we focused on the effect of spates on the caddisfly Agapetus fuscipes CURTIS (Trichoptera: Glossosomatidae) during different larval stages. A 2 year field study was performed in which we measured the discharge dynamics and population development of A. fuscipes in four lowland streams in The Netherlands. A stage-structured population model (i.e. StagePop) was used to test the impact of peak discharge on the different life stages, as larval instars 1–4 were not effectively sampled in the field. Four different mortality rates in response to spates were simulated, including a constant low, a constant high, a decreasing and an increasing impact per larval stage. This way, we were able to show a potential association between spates and population declines, where the stage-population model including decreasing impact by spates with increasing larval life stage most accurately described the population development of the larval instars 5–8. Focusing only on late instars could thus potentially result in underestimation of the effects of spates on this species. In conclusion, determination of responses of critical life stages to specific disturbances may help to identify the causes of the presence and absence of species, and thereby aid more effective management and restoration of degraded aquatic systems.
Modelling the present and futurewater level and discharge of the tidal betna river
Islam, M.M.M. ; Hofstra, Nynke ; Sokolova, Ekaterina - \ 2018
Geosciences 8 (2018)8. - ISSN 2076-3263
Discharge - Flood - General circulation models (GCM) - MIKE 21 FM model - Precipitation - Water level
Climate change, comprising of changes in precipitation patterns, higher temperatures and sea level rises, increases the likelihood of future flooding in the Betna River basin, Bangladesh. Hydrodynamic modellingwas performed to simulate the present and future water level and discharge for different scenarios using bias-corrected, downscaled data from two general circulation models. The modelling results indicated that, compared to the baseline year (2014–2015), the water level is expected to increase by 11–16% by the 2040s and 14–23% by the 2090s, and the monsoon daily maximum discharge is expected to increase by up to 13% by the 2040s and 21% by the 2090s. Sea level rise is mostly responsible for the increase in water level. The duration of water level exceedance of the established danger threshold and extreme discharge events can increase by up to half a month by the 2040s and above one month by the 2090s. The combined influence of the increased water level and discharge has the potential to cause major floods in the Betna River basin. The results of our study increase the knowledge base on climate change influence on water level and discharge at a local scale. This is valuable for water managers in flood-risk mitigation and water management.
Water-efficient zero-emission greenhouse crop production : A preliminary study
Beerling, E. ; Os, E. Van; Ruijven, J. Van; Janse, J. ; Lee, Andrew ; Blok, C. - \ 2017
In: International Symposium on New Technologies and Management for Greenhouses - GreenSys2015 International Society for Horticultural Science (Acta Horticulturae ) - ISBN 9789462611665 - p. 1133 - 1140.
Discharge - Drain water - Emission - Greenhouse horticulture - Nutrient solution - Plant protection products - Recycling - Soilless cultivation
Greenhouse cultivations are high input systems with respect to water and fertiliser usage. Worldwide increasing water shortages and competition for freshwater is raising the awareness that water use efficiency is a necessity in greenhouse horticulture. Releasing drain water from the greenhouse into the environment can also compromise surface and ground water quality due to the emissions of fertilisers and plant protection products. In soilless cultivation the nutrient solution can be recirculated; consequently they are highly efficient and sustainable production systems. Dutch growers have to realise zero emission by 2027 due to agreements made with government. However most are hesitant to fully recycle nutrient solutions, despite the many studies that have been conducted to resolve technical (installation) and physiological (growth) problems related to recycling drain water. In this study we demonstrate that with current best practice zero-emission crop production can become a reality. In the first trial (cucumber; July-November 2014) and up to the mid-season evaluation point of the second trial (sweet pepper; Dec-July 2015) no differences in production and fruit quality were found between the zero-emission cultivation and the reference cultivation grown to the agreed emission standards of 2015. Technology and cultivation strategy implemented are described and discussed and compared to common practice.
Effects of River Discharge and Land Use and Land Cover (LULC) on Water Quality Dynamics in Migina Catchment, Rwanda
Uwimana, Brigitte ; Dam, Anne van; Gettel, Gretchen ; Bigirimana, Bonfils ; Irvine, Kenneth - \ 2017
Environmental Management 60 (2017)3. - ISSN 0364-152X - p. 496 - 512.
Agriculture - Discharge - Land use - Nutrients - Water quality - Wetlands
Agricultural intensification may accelerate the loss of wetlands, increasing the concentrations of nutrients and sediments in downstream water bodies. The objective of this study was to assess the effects of land use and land cover and river discharge on water quality in the Migina catchment, southern Rwanda. Rainfall, discharge and water quality (total nitrogen, total phosphorus, total suspended solids, dissolved oxygen, conductivity, pH, and temperature) were measured in different periods from May 2009 to June 2013. In 2011, measurements were done at the outlets of 3 sub-catchments (Munyazi, Mukura and Akagera). Between May 2012 and May 2013 the measurements were done in 16 reaches of Munyazi dominated by rice, vegetables, grass/forest or ponds/reservoirs. Water quality was also measured during two rainfall events. Results showed seasonal trends in water quality associated with high water flows and farming activities. Across all sites, the total suspended solids related positively to discharge, increasing 2–8 times during high flow periods. Conductivity, temperature, dissolved oxygen, and pH decreased with increasing discharge, while total nitrogen and total phosphorus did not show a clear pattern. The total suspended solids concentrations were consistently higher downstream of reaches dominated by rice and vegetable farming. For total nitrogen and total phosphorus results were mixed, but suggesting higher concentration of total nitrogen and total phosphorus during the dry and early rainy (and farming) season, and then wash out during the rainy season, with subsequent dilution at the end of the rains. Rice and vegetable farming generate the transport of sediment as opposed to ponds/reservoir and grass/forest.
Modelling Discharge and Sediment Yield at Catchment Scale Using Connectivity Components
Masselink, Rens J.H. ; Keesstra, Saskia D. ; Temme, Arnaud J.A.M. ; Seeger, Manuel ; Giménez, Rafael ; Casalí, Javier - \ 2016
Land Degradation and Development 27 (2016)4. - ISSN 1085-3278 - p. 933 - 945.
Connectivity - Discharge - Model - N-Spain - Sediment yield
Knowledge about connectivity and what affects it, through space and time, is needed for taking appropriate action at the right place and/or time by stakeholders. Various conceptual frameworks for hydrological and sediment connectivity have been developed in recent years. For most of these frameworks, the objective was to conceptualise connectivity, not necessarily to infer it from measurements. Studies focussing on measurements of connectivity have so far not been done often. Because of lack of data on connectivity, few real-world data have been used in recent connectivity modelling studies. The aim of this study was to demonstrate that existing data can be used to assess governing factors of connectivity, and how these change over time. Data from three catchments in Navarre, Northern Spain, were used to assess factors that influence hydrologic and sediment connectivity. These factors were used as components in a linear model for discharge and suspended-sediment yield. Three components of connectivity were distinguished: topographical, biological and soil. Changes in the topographical component for the studied periods were considered relatively small, and, therefore, kept constant. Changes in the biological component were determined using the Normalised Difference Vegetation Index. Changes in the soil component were assessed using an Antecedent Precipitation Index. Nash-Sutcliffe model efficiency coefficients were between 0·49 through 0·62 for the discharge models and between 0·23 through 0·3 for the sediment-yield models. We recommend applying the model at smaller spatial scales than catchment scale to minimise the lumping of spatial variability in the components.