Droughts are recognised as environmental disasters, characterised by a slow development, high resilience, and non-structural impacts spread over large geographical areas. In recent decades, global warming has led to drier conditions and an increase in the frequency of these extreme events, making drought an increasingly severe phenomenon. The Mediterranean region is defined as a hotspot of climate change where droughts are increasing in frequency and intensity. Droughts impact numerous sectors, with agriculture identified as one of the most vulnerable, suffering significant crop losses during droughts. In this context, the exploration of effective drought management measures becomes essential to support food security and mitigate drought impacts. In this work, we assess the feasibility of implementing water storage expansion to collect precipitation in the Po River basin, an area vital to the country's agriculture and economy, located in between the Alpine and Mediterranean climates. We first analyse the spatial and temporal patterns of temperature and precipitation based on ERA5 reanalysis data covering a time horizon of 82 years from 1941 to 2022, followed by an analysis of the drought risk in the region according to the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Subsequently, we estimate the crop water requirement of agricultural lands based on the WATNEEDS model output. Finally, we compare the volumes of crop water requirement with the available water supplied by the precipitation in each sub-basin of the region. This comparison is carried out on both an annual and monthly basis, considering average and critical events of precipitation. This enables the identification of the operational drought hazard of basins, i.e. a condition in which the water supply can't fully meet demand. The results of the first analysis show that temperatures in the plain are higher and precipitation lower than in the mountains. Over time, temperatures have risen considerably, while precipitation is more variable, with alternating periods of positive and negative anomalies. The findings of the drought analysis according to SPI and SPEI indicate that the most vulnerable basins are located mainly in the western part of the region and only partly in the eastern side. The results of the operational drought analysis show that deficits between precipitation and crop water demands are not detected on an annual basis or considering the average monthly precipitation. Rather, they are observed in some critical precipitation conditions such as the 10th percentile or the worst monthly cases. This finding suggests how it might be possible to store water from precipitation in the months preceding the deficit condition and utilise it later to supply the required irrigation. The basins most exposed to the operational drought hazard, where deficits range from about 7 to more than 100 million cubic metres of water, are mainly located in the eastern part of the region, where agricultural demand is particularly high. This result differs from the outcome of the drought evaluation conducted using the SPI and SPEI indices. There is a partial agreement only regarding the eastern region, at high risk of operational drought, where significant frequency and intensity are present according to the SPI and SPEI indices. The western region, the most critical according to drought indices, does not show particular criticisms for operational drought hazard. Overall, these findings suggest that meteorological drought indices are not able to identify the regions mostly exposed to drought risks and determine the best placement of storage to mitigate the effects of droughts. Instead, the assessment should focus on the agricultural demand, with the highest values more widely spread towards the Po Delta.
Le magre idriche, o siccità, sono riconosciute come disastri ambientali caratterizzati da un’evoluzione graduale, elevata resilienza e impatti non strutturali distribuiti su vaste aree geografiche. Negli ultimi decenni, il riscaldamento globale ha portato a condizioni più secche e a un aumento della frequenza di questi eventi estremi, rendendo le magre un fenomeno sempre più grave. La regione mediterranea è definita come un hotspot del cambiamento climatico, dove le magre stanno aumentando in frequenza e intensità. La siccità ha un impatto su numerosi settori e l'agricoltura è considerata uno dei più vulnerabili, in quanto subisce perdite significative di raccolti durante questi eventi. In questo contesto, l'esplorazione di misure efficaci di gestione delle magre idriche diventa essenziale per sostenere la sicurezza alimentare e mitigare gli impatti della siccità. In questa tesi viene valutata la fattibilità di implementare l'espansione dello stoccaggio idrico per raccogliere le precipitazioni nel bacino del fiume Po, un'area vitale per l'agricoltura e l'economia del Paese, situata tra il clima alpino e quello mediterraneo. In primo luogo, vengono analizzate le tendenze spaziali e temporali di temperatura e precipitazione sulla base dei dati di rianalisi ERA5 che coprono un orizzonte temporale di 82 anni dal 1941 al 2022, seguiti da un'analisi del rischio di magra nella regione basato sugli indici Standardised Precipitation Index (SPI) e Standardised Precipitation Evapotranspiration Index (SPEI). Successivamente, viene stimato il fabbisogno idrico dei terreni agricoli sulla base dei risultati del modello WATNEEDS. Infine, i volumi di acqua richiesti dalle colture vengono confrontati con l'acqua disponibile fornita dalle precipitazioni, in ogni sottobacino della regione. Questo confronto viene effettuato sia su base annuale che mensile, considerando sia eventi medi che critici di precipitazione. Ciò consente di identificare il rischio di magra operativa dei bacini, ossia una condizione in cui l'approvvigionamento idrico non è in grado di soddisfare completamente la domanda. I risultati della prima analisi mostrano temperature più elevate e precipitazioni più scarse in pianura rispetto alle montagne. Nel corso del tempo, le temperature sono aumentate notevolmente, mentre le precipitazioni sono più variabili, con un'alternanza di periodi caratterizzati da anomalie positive o negative. I risultati dell'analisi di magra basata sugli indici SPI e SPEI indicano che i bacini più vulnerabili si trovano principalmente nella parte occidentale della regione e solo in parte in quella orientale. La valutazione della magra operativa mostra che i deficit tra le precipitazioni e le richieste idriche delle colture non vengono rilevati su base annuale o considerando le precipitazioni medie mensili. Piuttosto, vengono osservati in condizioni di precipitazioni più critiche, come il 10° percentile o i casi mensili peggiori. Questo dato suggerisce come sia possibile immagazzinare l'acqua delle precipitazioni nei mesi precedenti la condizione di deficit e utilizzarla successivamente per fornire l'irrigazione necessaria. I bacini più esposti al rischio di magra operativa, dove i deficit variano da circa 7 a oltre 100 milioni di metri cubi d'acqua, si trovano principalmente nella parte orientale della regione, dove la domanda agricola è particolarmente elevata. Questo risultato si discosta dall'esito della valutazione di magra condotta utilizzando gli indici SPI e SPEI. È presente un accordo parziale solo per quanto riguarda la regione orientale, ad alto rischio di magra operativa, dove sono presenti frequenze e intensità significative secondo gli indici SPI e SPEI. La regione occidentale, la più critica secondo gli indici di magra, non mostra invece particolari criticità per il rischio di magra operativa. Nel complesso, questi risultati suggeriscono che gli indici di magra meteorologica non sono particolarmente adatti ad identificare le regioni più esposte al rischio di magra e a determinare il miglior posizionamento dello stoccaggio per mitigare gli effetti degli eventi di magra. La valutazione dovrebbe invece concentrarsi sulla domanda agricola, con i valori più alti maggiormente distribuiti verso il Delta del Po.
Enhancing droughts resilience via expansion of water storage infrastructures
Sica, Giorgia
2022/2023
Abstract
Droughts are recognised as environmental disasters, characterised by a slow development, high resilience, and non-structural impacts spread over large geographical areas. In recent decades, global warming has led to drier conditions and an increase in the frequency of these extreme events, making drought an increasingly severe phenomenon. The Mediterranean region is defined as a hotspot of climate change where droughts are increasing in frequency and intensity. Droughts impact numerous sectors, with agriculture identified as one of the most vulnerable, suffering significant crop losses during droughts. In this context, the exploration of effective drought management measures becomes essential to support food security and mitigate drought impacts. In this work, we assess the feasibility of implementing water storage expansion to collect precipitation in the Po River basin, an area vital to the country's agriculture and economy, located in between the Alpine and Mediterranean climates. We first analyse the spatial and temporal patterns of temperature and precipitation based on ERA5 reanalysis data covering a time horizon of 82 years from 1941 to 2022, followed by an analysis of the drought risk in the region according to the Standardised Precipitation Index (SPI) and the Standardised Precipitation Evapotranspiration Index (SPEI). Subsequently, we estimate the crop water requirement of agricultural lands based on the WATNEEDS model output. Finally, we compare the volumes of crop water requirement with the available water supplied by the precipitation in each sub-basin of the region. This comparison is carried out on both an annual and monthly basis, considering average and critical events of precipitation. This enables the identification of the operational drought hazard of basins, i.e. a condition in which the water supply can't fully meet demand. The results of the first analysis show that temperatures in the plain are higher and precipitation lower than in the mountains. Over time, temperatures have risen considerably, while precipitation is more variable, with alternating periods of positive and negative anomalies. The findings of the drought analysis according to SPI and SPEI indicate that the most vulnerable basins are located mainly in the western part of the region and only partly in the eastern side. The results of the operational drought analysis show that deficits between precipitation and crop water demands are not detected on an annual basis or considering the average monthly precipitation. Rather, they are observed in some critical precipitation conditions such as the 10th percentile or the worst monthly cases. This finding suggests how it might be possible to store water from precipitation in the months preceding the deficit condition and utilise it later to supply the required irrigation. The basins most exposed to the operational drought hazard, where deficits range from about 7 to more than 100 million cubic metres of water, are mainly located in the eastern part of the region, where agricultural demand is particularly high. This result differs from the outcome of the drought evaluation conducted using the SPI and SPEI indices. There is a partial agreement only regarding the eastern region, at high risk of operational drought, where significant frequency and intensity are present according to the SPI and SPEI indices. The western region, the most critical according to drought indices, does not show particular criticisms for operational drought hazard. Overall, these findings suggest that meteorological drought indices are not able to identify the regions mostly exposed to drought risks and determine the best placement of storage to mitigate the effects of droughts. Instead, the assessment should focus on the agricultural demand, with the highest values more widely spread towards the Po Delta.| File | Dimensione | Formato | |
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https://hdl.handle.net/10589/214637