Ticino River Research Articles

Birth and Growth of a "Silicon Valley by the Ticino River"

I had the opportunity to meet Prof. Rinaldo Castello in the mid-80s of the last century, shortly after he joined the Department of Electrical Engineering of the University of Pavia.

Seasonal evolution of the zooplankton community in two riverine wetlands of the Ticino River (Lombardy, Northern Italy)

Riverine wetlands are vulnerable ecotonal environments and are often threatened by human activities. A project supported by the Cariplo Foundation, called “Ecological and hydromorphological requalification of wetlands in the Ticino area around Pavia” (South-East Lombardy, Northern Italy), was started in 2010 with the aim of improving the chemical, bio-ecological and hydrological conditions of these wetlands. In line with the aim of this project, we selected two wetlands near the main course of the Ticino River for investigation, one of which is impacted by a combined sewer overflow from the sewerage networks which is always active (San Lanfranco (SL) wetland), whereas the other (Topo (TO) oxbow lake) is less directly impacted by anthropogenic activities. In this paper, we report the ecological situation of these two wetlands before the requalification process by investigating the way the zooplankton assemblages, considered as bio-indicators, respond to anthropogenic pressure. Overall, we collected 19 taxa : 4 cladocerans, 1 copepod and 14 rotifers. In the TO oxbow lake, we found a stable community, dominated by the cladoceran Bosmina longirostris. By comparison, in the SL wetland we found a pioneer community, dominated by the juvenile stage of the copepod Thermocyclops dybowskii . The SL wetland was shown to be most urgently in need of improvement and is therefore first in line for requalification, whereas the TO oxbow lake needs less drastic measures to ensure the long-term ecological functioning of the aquatic environment. After these requalification activities, a systematic zooplankton survey will be carried out to monitor the evolution of the riverine wetlands.

Biodiversity loss in a small riverine wetland of the Ticino river (Lombardia, Northern Italy)

Wetlands are heterogeneous habitats that include various biotopes with different formations, structures and geographical positions. There are many small wetlands in the Ticino river area around Pavia (Lombardia, Northern Italy), many of which evolve naturally and originate from abandoned riverbeds, isolated river meanders, oxbow lakes or small ponds fed by terrace springs or underground waters. We decided to consider the evolution of one of these wetlands, namely the Topo oxbow lake. It had previously been studied 24 years ago (1988-1990), so we compared the results with those collected during a recent one-year investigation (June 2011-June 2012) on the following aspects: dimensions, hydrometric level fluctuation and bathymetry, principal chemical-physical parameters, hygrophytic and aquatic vegetation, and zooplankton communities. The resulting geo-morphological and biotic community changes are typical of riverine wetlands, thus supporting the hypothesis that this oxbow lake is following its natural evolution. Morphological changes in the oxbow lake should influence its biotic communities: the high plant biomass that existed in the past could be considered to have been the first step towards eutrophication, but the oxbow lake remained at mesotrophic level due to high biodiversity and dissolved oxygen levels in the water. Nowadays, the lower biodiversity in aquatic plants and zooplankton suggests a trophic level shift towards eutrophication due to the endogenous evolution of the oxbow lake. However, these ideas are not supported by the physical and chemical parameters of the water which indicate that the oxbow lake is still at mesotrophic level. We would suggest planning a gentle restoration of this biotope, with the aim of rejuvenating the physical habitat to ensure the long-term ecological functioning of the aquatic environment.

Tree‐based iterative input variable selection for hydrological modeling

Input variable selection is an important issue associated with the development of several hydrological applications. Determining the optimal input vector from a large set of candidates to characterize a preselected output might result in a more accurate, parsimonious, and, possibly, physically interpretable model of the natural process. In the hydrological context, the modeled system often exhibits nonlinear dynamics and multiple interrelated variables. Moreover, the number of candidate inputs can be very large and redundant, especially when the model reproduces the spatial variability of the physical process. The ideal input selection algorithm should therefore provide modeling flexibility, computational efficiency in dealing with high dimension data set, scalability with respect to input dimensionality and minimum redundancy. In this paper, we propose the tree‐based iterative input variable selection algorithm, a novel hybrid model‐based/model‐free approach specifically designed to fulfill these four requirements. The algorithm structure provides robustness against redundancy, while the tree‐based nature of the underlying model ensures the other key properties. The approach is first tested on a well‐known benchmark case study to validate its accuracy and subsequently applied to a real‐world streamflow prediction problem in the upper Ticino River Basin (Switzerland). Results indicate that the algorithm is capable of selecting the most significant and nonredundant inputs in different testing conditions, including the real‐world large data set characterized by the presence of several redundant variables. This permits one to identify a compact representation of the observational data set, which is key to improving the model performance and assisting with the interpretation of the underlying physical processes.

A phytosociological survey of the Corynephorus canescens (L.) Beauv. communities of Italy

In Italy, Corynephorus communities are distributed along the medium course of the Ticino river and Sesia river and the internal sand dunes of Lomellina (through the Vercelli, Novara and Pavia provinces); these stations represent the southern limit of European distribution of this habitat. A phytosociological study was carried out to gain better knowledge of their composition; of their affinity or diversity against the central European communities; of their distribution and of the main threats to their conservation. Original and literature relevés (114) were elaborated producing a cluster analysis; correspondence analysis (CA), principal component analysis and Kruskal–Wallis test were carried on to characterize the clusters of relevés taking into consideration biological forms, chorological groups, Ellenberg indicator values and floristic groups. Italian Corynephorus communities can be attributed to the following syntaxa: Spergulo vernalis-Corynephoretum canescentis, Spergulo vernalis-Corynephoretum canescentis cladonietosum, Spergulo vernalis-Corynephoretum canescentis silenetosum nutantis and Spergulo vernalis-Corynephoretum canescentis artemisietosum campestris. Italian Corynephorus communities are included in the Habitat 2330 of the EU Habitat Directive. They are threatened by different factors (such as restricted areas of occurrence, alien plant invasion and natural dynamics) and they need to be managed if we want to conserve them.

Valuing hydrological alteration in multi-objective water resources management

Summary The management of water through the impoundment of rivers by dams and reservoirs is necessary to support key human activities such as hydropower production, agriculture and flood risk mitigation. Advances in multi-objective optimization techniques and ever growing computing power make it possible to design reservoir operating policies that represent Pareto-optimal tradeoffs between multiple interests. On the one hand, such optimization methods can enhance performances of commonly targeted objectives (such as hydropower production or water supply), on the other hand they risk strongly penalizing all the interests not directly (i.e. mathematically) included in the optimization algorithm. The alteration of the downstream hydrological regime is a well established cause of ecological degradation and its evaluation and rehabilitation is commonly required by recent legislation (as the Water Framework Directive in Europe). However, it is rarely embedded in reservoir optimization routines and, even when explicitly considered, the criteria adopted for its evaluation are doubted and not commonly trusted, undermining the possibility of real implementation of environmentally friendly policies. The main challenges in defining and assessing hydrological alterations are: how to define a reference state (referencing); how to define criteria upon which to build mathematical indicators of alteration (measuring); and finally how to aggregate the indicators in a single evaluation index (valuing) that can serve as objective function in the optimization problem. This paper aims to address these issues by: (i) discussing the benefits and constrains of different approaches to referencing, measuring and valuing hydrological alteration; (ii) testing two alternative indices of hydrological alteration, one based on the established framework of Indicators of Hydrological Alteration ( Richter et al., 1996 ), and one satisfying the mathematical properties required by widely used optimization methods based on dynamic programming; (iii) demonstrating and discussing these indices by application River Ticino, in Italy; (iv) providing a framework to effectively include hydrological alteration within reservoir operation optimization.

Distribution and diet of reintroduced otters ( Lutra lutra ) on the river Ticino (northern Italy)

Abstract On the River Ticino (northern Italy), the release of a pair of otters Lutra lutra in 1997, followed by the escape of an otter female with her cub in 2001, allowed the establishment of a small population. In summer 2008, a survey has been carried out by the standard method to draw a first picture of current otter distribution. Some data about otter diet have been obtained through the analysis of 36 spraints. Otter presence has been recorded for 3 out of 10 sampling stations, corresponding to a 2.6 km long stretch of the river. Considering only this stretch, the mean number of sprainting sites per 100 m was 0.10, while the mean number of spraints per 100 m was 0.19. Fish - mainly Salmo trutta , Perca fluviatilis , Phoxinus phoxinus and Chondrostoma genei -, formed the bulk of otters’ diet. The prosecution of the reintroduction project requires an updated feasibility study which provides for management actions aimed to favour the expansion of the species in northern Italy. Riassunto Distribuzione e dieta delle lontre Lutra lutra reintrodotte sul fiume Ticino (Italia settentrionale). Il rilascio, nel 1997, di una coppia di lontra Lutra lutra sul fiume Ticino (Italia settentrionale), unitamente alla fuga, nel 2001, di una femmina con i piccoli, ha portato alla formazione di una piccola popolazione. Per ottenere un primo quadro dell’attuale distribuzione della specie, nell’estate 2008 e stata condotta un’indagine tramite il metodo standard. Inoltre, dall’analisi di 36 feci, sono stati ottenuti alcuni dati sulla dieta. La presenza della lontra e stata accertata per 3 delle 10 stazioni monitorate, corrispondenti a un tratto di fiume pari a 2.6 km. Considerando solo le stazioni positive, il numero medio di siti di marcamento per 100 m e stato pari a 0,10, corrispondente a 0,23 feci per 100 m. I pesci – in particolare Salmo trutta , Perca fluviatilis , Phoxinus phoxinus and Chondrostoma genei -, rappresentano la principale risorsa trofica della lontra. La prosecuzione del progetto di reintroduzione richiede uno studio di fattibilita che contempli interventi gestionali atti a favorire l’espansione della specie in Italia settentrionale.

Cycling pp'DDT and pp'DDE at a watershed scale: the case of Lago Maggiore (Italy)

A point source of DDT pollution of industrial origin, discovered in 1996 in Lago Maggiore, the second largest (212 km 2 ) and deepest (373 m) lake in Italy, created concern for wildlife and human health because contamination in some fish species exceeded the threshold for human consumption, even though the concentrations measured in the water were much lower than the legal requirements for drinking purposes. Some precautionary measures were undertaken to prevent DDT runoff from the industrial site to the lake but soil restoration had not yet been carried out. The first study to quantify land based sources of DDT homologue pollution was performed in 1998 by sampling all the main tributaries monthly in order to evaluate the annual load to the lake. From May 2001 to May 2002, the study was repeated in order to evaluate the degree of recovery. In this work we compared the results of that survey with those of a more recent campaign carried out from May 2001 to May 2002, concluding that land based sources are still relevant for pp’DDE, the most stable metabolite of pp’DDT, while they are negligible for the parent compound. Furthermore, the Toce River, receiving the soil runoff of the industrial area, was found to give the greatest contribution of DDT and DDE load to the lake in the past campaign, while its load drastically decreased in 2001-2002 in the case of pp’DDT, being comparable to that of Ticino River(the second biggest river of the Lago Maggiore basin, which rises in the St. Gotthard Massif of the Swiss Alpes). Air transport and cold condensation are very likely responsible for trapping DDT and DDE in high mountain glaciers, which represent a secondary pollution source.

Air, Water and Vacuum Pluviation of Sand Specimens for the Triaxial Apparatus

ABSTRACT A device is presented for reconstituting sand specimens directly onto the triaxial apparatus by pluviation in air, water or under vacuum. The sand is delivered by means of an uniform rain covering the whole specimen cross section and target density is achieved by changing fall height and depositional intensity. The apparatus was calibrated using Ticino River sand, for which water and vacuum pluviations provided the lowest and highest densities, respectively. Whilst the density of loose samples was similar to that obtained using Kolbuszewski (1948) and ASTM minimum density methods, much denser specimens were obtained with vacuum pluviations as compared to vibration compaction methods (similar to ASTM maximum density method). The resulting maximum relative density, referred to the limits from standard tests, was as high as 140%. Water pluviation density is independent of both depositional intensity and fall height. For other target density best results in terms of sample uniformity are achieved by vacuum pluviation with an appropriate selection of depositional intensity and fall height. This also provides an extremely high reproducibility of target density.

The nematode community of two Italian rivers (Taro and Ticino)

AbstractThe Taro and Ticino rivers were sampled (maximum 15 cm depth) for nematodes during 1 year at three sites for each river and some ecological parameters were measured. The yearly mean abundance of nematodes in the river Taro was 23 individuals/10 cm2 and in the river Ticino 79 individuals/10 cm2. In the two rivers five to 15 and three to ten species, respectively, were found. The highest station (Taro 1) of the river Taro was significantly different from all the other Taro and Ticino stations both for number and species composition: bacterial feeders were the dominant group in Taro 1 (mean Maturity Index (MI) was 2.25), whereas unicellular eukaryote feeders dominated the other Taro and Ticino sites (mean MI of 2.85). Chromadorina bioculata was the most common species in both rivers, except at Taro 1, where Eumonhystera dispar dominated. Significant correlations were found between conductivity and unicellular eukaryote feeders and bacterial feeders. For the first time the Distinctness Index δ+ is used for freshwater nematodes. Comparing our communities with other Italian rivers (data taken from the literature), we detected significant differences between polluted and not polluted habitats.

Evaluation of enzyme biomarkers in freshwater invertebrates from Taro and Ticino river, Italy

Benthic macroinvertebrates are an essential component of freshwater environments. The ecotoxicological risk of benthic communities, estimated through the assay of biochemical markers, can be used as an early warning signal for environment alterations. In this work the activities of a number of enzymes, regarded as potential biomarker of exposure to pollutants (catalase, acetylcholinesterase, glutathione-S-transferase) was determined in homogenates of whole organisms. Specimens were collected in the rivers Taro and Ticino, northern Italy, in stony bottom reaches in five and three stations respectively. The orders of aquatic Insects Diptera, Plecoptera, Odonata, Ephemeroptera and Trichoptera, the Crustacea Amphipoda, and Annelida Oligochaeta were examined. Additional enzymes, such as NADP-dependent malate dehydrogenase, isocitric dehydrogenase, glucose-6phosphate dehydrogenase, alcohol dehydrogenase, and lactate dehydrogenase were considered in the study. Results emphasize significant differences among taxa concerning the specific activity of most enzymes.

Development of molecular markers to assess the level of introgression of Populus tremula into P. alba natural populations

AbstractMorphological traits traditionally adopted to discriminate between Populus alba L. and P. tremula L. have frequently led to misclassifi‐cation of their spontaneous hybrid P. × canescens Sm. Moreover, they may not be of any help in cases of spontaneous backcross phenomena. These limitations can be overcome by molecular markers, which are not environmentally influenced nor subjectively assessed. In this study, the effectiveness of amplified fragment length polymorphism (AFLP) and simple sequence repeat (SSR) markers in species and hybrid discrimination was evaluated by analysing a set of reference samples of P. alba, P. tremula and P. × canescens. Species‐specific and species‐indicative AFLPs, as well as diagnostic SSR alleles, were recorded in both P. alba and P. tremula reference samples. The results allowed a clear distinction between the two poplar species and their hybrid. Using these diagnostic markers, a natural population of P. alba trees sampled along the Ticino river basin in northern Italy was analysed, and P. × canescens individuals, intermingled with P. alba trees, were detected.

Ecological impacts of hydroelectric power production on the River Ticino. Part 2: Effects on the larval development of the dominant benthic macroinvertebrate (Allogamus auricollis, Trichoptera)

In Switzerland most major rivers are utilised for hydroelectric power production. As a consequence their temperature regime is severely altered. Because temperature is an ecological key parameter, substantial ecological consequences may be expected. This study was carried out to analyse the effects of such temperature alterations on the growth and development of the dominant benthic insect. Growth and development of Allogamus auricollis (Trichoptera: Limnephilidae) populations from 13 locations along the River Ticino with very different temperature regimes were investigated between March 1999 and August 2001. To separate temperature effects from possible effects of food limitation, a rearing experiment was also conducted. In two laboratory flumes, where excess food was supplied, caddisfly larvae were reared between February and July 2001 under temperature conditions resembling the coldest and the warmest field site, respectively. Whereas larval growth of A. auricollis in the River Ticino appeared to be mostly independent of prevalent temperatures, it seemed to be temperature controlled in the laboratory, suggesting that larval growth and development of field populations may be food-limited. This assumption is supported by the finding that larval dry weight in the flumes was three times higher than in the corresponding field populations at the end of the rearing experiment. In summary, it seems that larval development of A. auricollis is hardly affected by the temperature alterations due to hydroelectric power production. However, it is suspected that the dominance of this caddisfly per se is probably a consequence of the human induced temperature alterations.

Ecological impacts of hydroelectric power production on the River Ticino. Part 1: Thermal effects

As a consequence of widespread hydroelectric power production, the temperature regime of most major rivers in Switzerland is severely altered. This study was conducted to describe the impacts of a complex, yet typical hydroelectric power scheme in the Swiss Alps on the temperature regime of the utilised river. Between September 1998 and October 2001, temperature was continuously recorded at 20 different locations along the River Ticino (i.e. upstream, downstream, and in the water outlet of every major hydropower installation). Average temperatures on water abstraction sections were higher than natural during summer and lower than natural during winter, but annual temperature sum remained unaltered. Temperature amplitudes exceeded the natural situation in both seasons. Below water releases, in contrast, average temperature was somewhat higher than natural in winter, but much cooler than natural in summer, resulting in a substantial (-59%) annual heat deficit. Temperature fluctuations were weak but much more frequent than natural. It is suggested to assess the thermal impact of hydroelectric power production using the frequency of these temperature fluctuations.

Rana dalmatina and R. latastei: Habitat selection, fluctuation in egg clutch deposition and response to exceptional floods in northern Italy

A ten year census was carried out on Rana dalmatina and R. latastei egg masses deposited in 36 reproductive sites in a 10‐hectare area, subject to periodic flooding, on the banks of the Ticino River. The vegetation type surrounding reproductive sites was noted. There were no signs of decline in the populations of either frog species. The number of egg clutches fluctuated widely from year to year but no correlation between clutch number and either flooding or climate parameters were detected. R. dalmatina preferred partly open areas for reproductive sites, whereas R. latastei selected areas characterized by hygrophilous vegetation and a high tree canopy.

Estimating the benefits of low flow alleviation in rivers: the case of the Ticino River

In Switzerland 60% of electricity is produced by hydropower plants. The construction and operation of these plants determine some negative environmental externalities, such as diminishing groundwater levels and spring flows, and a reduction in river flow, which can severely curtail recreational and fishing activities. This study concentrates on an ex-ante appraisal of the monetary benefits resulting from an enhancement of river flow for recreational fishing purposes. A comparison of estimates of these benefits to the corresponding costs, in terms of loss of electricity production, incurred by hydropower plants to alleviate low flows may be useful for policy makers. For this analysis, as suggested by Layman et al. (Land Economics 72, pp. 113-128, 1996), the Travel Cost Method (TCM) is extended to estimate the economic value of recreational fishing in the Ticino River (the most important river of the Canton Ticino) under existing and hypothetical river flow conditions. Anglers were asked to state how the number of trips they took to the Ticino River would change if an increase in the river flow was imposed on the hydropower plants. The empirical results show that an enhancement of river flow increases the annual consumer surplus for a typical angler by approximately 440 SFr.

Water quality as a determinant of the composition of fish parasite communities

To investigate the relationship between fish parasite communities and water quality level, metazoan parasites were examined in 157 specimens of chub (Leuciscus cephalus L.), sampled in four lowland water courses (northern Italy): Ticino river (unpolluted), Naviglio Pavese Canal (slightly polluted), Lambro river near the Merone village (polluted) and near Monza (severely polluted). Dactylogyrus vistulae, Paradiplozoon ergensi, Bucephalus polymorphus, Acanthocephalus anguillae and larval stages of Tylodelphys clavata were found in all the sampled sites. The distribution of Lamproglena pulchella and Pomphorhynchus laevis was limited to the unpolluted and slightly polluted river sectors, while Asymphylodora tincae, glochidia, along with larval stages of Diplostomum spathaceum, were absent in the severely polluted site. The variability of the calculated infection indices (prevalence, mean abundance and mean intensity), the degree of interactivity among parasites, as well as parameters of species richness and diversity suggest that the structure of parasite communities are affected by the water contamination level.

Anisotropy of Small Strain Stiffness of Ticino and Kenya Sands from Seismic Wave Propagation Measured in Triaxial Testing

The small strain stiffness and anisotropic nature of two sands with different geological origin have been determined via laboratory seismic tests performed in a triaxial cell. Dry triaxial reconstituted specimens of Ticino river silica sand (TS) and of Kenya carbonatic sand (KS) were subjected to isotropic and anisotropic states of effective stress; then both shear and constrained compression waves were propagated in vertical, horizontal and oblique directions by means of five couples of piezoelectric transducers especially arranged in the specimens. The propagated compression and shear waves allow the assessment of the constrained Mo and shear Go moduli respectively, at very small strains where, as a first approximation many soils can be assumed, from an engineering point of view, to behave as an elastic cross-anisotropic medium with a vertical axis of symmetry. This paper, after a brief description of the novel measuring technique adopted and of the tested materials, summarises the test results and their interpretation in order to separate the effects of the fabric anisotropy from those produced by the state of effective stresses on soil stiffness. The stiffness and anisotropic response of the two tested sands are compared. Finally the results enable us to establish five independent constants of the cross-anisotropic elasticity model, which appears to be appropriate to reproduce the behaviour at small strain of the two sands.

Using macroinvertebrate species assemblages to identify river channel habitat units: an application of the functional habitats concept to a large, unpolluted Italian river (River Ticino, northern Italy)

The functional habitat concept was applied to a large Italian river for the first time. The characteristically wide range of hydraulic conditions present in this river (compared to previously-studied small, lowland, English rivers) were expected to be of central importance to biota and, therefore, to habitat definition. TWINSPAN analysis of the invertebrate assemblages sampled in the Ticino river identified five distinct habitats: two habitats in lotic areas (run-riffle and macrophytes in current), two along the river margins (with and without macrophytes) and one in backwater areas. These correspond to five of the functional habitats identified in U.K. lowland rivers. Each of these five functional habitats could be defined either in terms of hydraulics, substratum and/or presence/absence of macrophytes. Representative taxa are presented for each habitat and community structure discussed. Macrophyte and run-riffle habitats supported the most heterogeneous and abundant benthic fauna. No match was found between replicates grouped by invertebrate assemblage (the five functional habitats identified by TWINSPAN) and the grouping of the same replicates by PCA, carried out on the physical data matrix. While obvious velocity differences were found between the functional habitats, of particular note was the fact that the Froude number did not show any clear association with habitat type. In the future, improved river management will follow improved understanding of river habitats.

Populations of acanthocephalus anguillaePomphorhynchus laevis in rivers with different pollution levels

The distribution of two acanthocephalan species (Pomphorhynchus laevisAcanthocephalus anguillae) in the chub (Leuciscus cephalus) was studied in four river reaches characterized by different levels of pollution: the River Ticino near Abbiategrasso (unpolluted), the Naviglio Grande Canal, in Milano (slightly polluted), the River Lambro near Merone village (polluted) and the River Lambro near Monza (severely polluted).Pomphorhynchus laevis was restricted to the unpolluted and the slightly polluted sites, while the intensity of A. anguillae increased proportionally to water pollution. These differences were partially explained by the variation in abundance of their intermediate hosts (Echinogammarus stammeri for P. laevisAsellus aquaticus for A. anguillae). Data on the occurrence of P. laevis and A. anguillae showed a significant negative binomial frequency distribution, suggesting their tendency to be aggregated within the host populations of L. cephalus.