Josep Pascual

Global warming-enhanced stratification and mass mortality events in the Mediterranean

Summer conditions in the Mediterranean Sea are characterized by high temperatures and low food availability. This leads to “summer dormancy” in many benthic suspension feeders due to energetic constraints. Analysis of the most recent 33-year temperature time series demonstrated enhanced stratification due to global warming, which produced a ≈40% lengthening of summer conditions. Many biological processes are expected to be affected by this trend, culminating in such events as mass mortality of invertebrates. Climatic anomalies concomitant with the occurrence of these events represent prolonged exposure to warmer summer conditions coupled with reduced food resources. Simulation of the effects of these conditions on a model organism demonstrated a biomass loss of >35%. Losses of this magnitude result in mortality similar to that noted in field observations during mass mortality events. These results indicate that temperature anomalies are the underlying cause of the events, with energetic constraints serving as the main triggering mechanism.

Leakage isolation using pressure sensitivity analysis in water distribution networks: Application to the Barcelona case study

Abstract Leaks are present to some extent in all water-distribution systems. This paper proposes a leakage localisation method based on the pressure measurements and pressure sensitivity analysis of nodes in a network. The sensitivity analysis using analytical tools is not a trivial job in a real network because the huge non-explicit non-linear systems of equation that describe its dynamics. Simulations of the network in presence and absence of leakage may provide an approximation of this sensitivity. This matrix is binarised using a threshold independent of the node. The binary matrix is assumed as a signature matrix for leakages. However, there is a trade-off between the resolution of the leakage isolation procedure and the number of available pressure sensors. In order to maximise the isolability with a reasonable number of sensors, an optimal sensor placement methodology, based on genetic algorithms, is also proposed. This methodology has been developed for Barcelona Network using Piccolo simulator. The sensor placement and the leakage detection and localization methodologies are applied to district management areas (DMA).

Methodology to Detect and Isolate Water Losses in Water Hydraulic Networks: Application to Barcelona Water Network

Abstract This paper presents a methodology to detect real water losses in urban water networks. The proposed method is based on the combined use of the DMA economical water balance confidence intervals for a period of time longer than a month (a trimester, semester or year) with appropriated night flow ratio intervals. This method allows distinguishing between real and apparent water losses in a given DMA. The use of uncertainty models allows taking into account measurement uncertainty of the flow data sensors. The use of different periods of time allows the stabilization of the results. This methodology is illustrated in a DMA of the Barcelona water distribution network using real data.