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PGBSDM Development and Application

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PGBSDM Development and Application Development of a Group Built Coupled Physical – Socio- Economic Modelling Framework for Soil Salinity Management in Agricultural Watersheds in Developing Countries By Muhammad Azhar Inam Baig Department of Bioresource Engineering McGill University, Montreal A thesis submitted to McGill University in partial fulfillment of the requirements of the degree of Doctor of Philosophy © Azhar Baig, 2017 i ABSTRACT Stakeholder involvement in environmental modeling has gained considerable importance over the past twenty years. However, many water resource planning and management frameworks encounter significant challenges when trying to develop tools that do not require significant funding, time, or expertise and that facilitate stakeholder engagement in developing countries. This study aims to address such challenges by developing a stepwise participatory modeling framework to link physically-based models with stakeholder-assisted socio-economic models in the context of developing countries, using the Rechna Doab region of Pakistan as a case study area. Participatory system dynamics models (PSDM) were developed under constraints of limited expertise and financial and time resources by contacting potential stakeholder (e.g. local farmers, experts, government officials) and representing their views and policy options in the form of qualitative causal loop diagrams (CLDs). A holistic qualitative model of the watershed system was created by merging these individual causal loop diagrams. Meaningfully including stakeholder contributions in the modeling process helps incorporate the ideas and knowledge of local key stakeholders, integrates physical and socio-economic components within a watershed or sub- watershed, and improves model boundaries and completeness by ensuring that all relevant issues and views are addressed. The key physical and socio-economic processes were identified from the stakeholder-built CLDs. The socio-economic components were modeled through distributed submodules in a Group-Built System Dynamics Model (GBSDM). The distributed submodules represented canal seepage, surface storage, irrigation application and distribution, groundwater extraction, effective rainfall and runoff, irrigation efficiency improvement, agriculture water demand, and farm income. Feedbacks between the distributed submodules describe the interactions between them and allow for simulation of the behavior of the whole system at the watershed scale. The recommended structural and behavior validity tests were then employed to test and build confidence in the modeling system. The physical components of the CLDs were modeled through the Spatial Agro-Hydro- Salinity Model (SAHYSMOD), a distributed model that simulates groundwater changes as well as salt and water movement within the crop root zone at the watershed scale. The model was calibrated (1983-1988) and validated (1998-2003) over two five-year periods through comparison of observed and simulated groundwater levels. The model simulated groundwater elevation ii accurately with observed R2 values of 0.906 and 0.925, Nash–Sutcliffe model efficiencies of 0.812 and 0.873, and mean errors of 0.436 and 0.486 for the calibration and validation periods, respectively. Uncertainty and sensitivity analyses performed on the model using Generalised Likelihood Uncertainty Estimation (GLUE) estimated that 70% of the observed data falls within the 95% and 5% uncertainty bounds. These results indicate a good approximation of selected calibrating parameter ranges. Furthermore, the sensitivity analysis found groundwater extraction, hydraulic conductivity, application efficiency, and effective porosity to be the most sensitive parameters. GBSDM and SAHYSMOD were linked using the component modeling approach. Vensim Dynamic Link Libraries (DLL), python, and Visual Basic for Application (VBA) in MS Excel were used as linking tools. MS Excel was used as the wrapper to exchange information between the socio-economic and physical system components. Use of Excel as a wrapper increases model transparency and provides the opportunity for end users to manipulate data and evaluate policies. Both models exchange their output at a seasonal time step throughout the time period from 1980 to 2010. Six scenarios, including a base case scenario, one past implemented policy (i.e. Salinity Control and Reclamation Project (SCARP)), and various alternative management options for improving and reallocating canal water supply were tested. Spatial and temporal maps of changes in soil salinity, farm income, and water availability were prepared to evaluate the effects of the tested management options at the watershed scale. Policies were also evaluated for economic and environmental trade-offs through various performance indicators such as soil salinity, water availability, farm income and groundwater drawdown. The results clearly showed that canal lining and reallocating irrigation supplies had the potential to improve salt-affected areas. However, canal lining requires government support in the form of subsidies. The initial years of simulation suggest SCARP is the best management option although it might have positive impacts only if implemented intermittently. The continuous operation of SCARP may cause increased salt concentrations in the crop root zone due to secondary salinization. The SCARP policy results were in agreement with past SCARP monitoring studies. The overall benefits of the proposed coupled model (P-GBSDM) are the provision of additional strengths to SAHYSMOD by incorporating socio-economic processes through stakeholder engagement. Furthermore, the developed integrated model is capable of performing analyses that SAHYSMOD was not able to simulate, such as changes in farm income, spatial predictions of water availability, and the evaluation of economic and environmental trade-offs. iii RÉSUMÉ Le nombre d’intervenants dans la modélisation de l'environnement a augmenté considérablement au cours des vingt dernières années. De nombreux programmes de planification et de gestion des ressources en eau font cependant face à d’importants défis lorsqu’ils essayent de développer des méthodes de gestion de l’environnement dans les pays en développement. Ces défis sont exacerbés par le manque de méthodes demandant peu d’investissements de temps, de finances, ou de compétences en modélisation. La présente étude vise à relever ces défis en développant un cadre de modélisation par étapes s’appuyant sur un modèle physique complémenté par un modèle socio-économique fourni par les parties prenantes, ceci pour la région Rechna Doab du Pakistan. Des modèles des dynamiques des systèmes participatifs (MDSP) ont été développés sous des conditions de compétences, ressources financières et temps limités. Ils ont été développés en communiquant avec les acteurs potentiels (par exemple, les fermiers locaux, les experts et les représentants du gouvernement) et en représentant leurs points de vue et leurs idées pour des politiques potentielles sous la forme de diagrammes de boucles causales (DBC). Un modèle qualitatif de l'ensemble du système du bassin versant a été créé en combinant les diagrammes causals de chaque acteur. En prenant en compte de manière rigoureuse les contributions de chaque partie prenante dans le processus de modélisation, on peut ainsi s’assurer que les idées et les connaissances de ces acteurs locaux soient incluses, intégrant ainsi les composants physiques et socio-économiques dans l’étude d’un bassin versant. Cette approche améliore aussi les limites du modèle et son exhaustivité en veillant à ce que toutes les questions pertinentes et points de vue soient pris en compte. Les processus physiques et socio-économiques clés ont été identifiés dans les DBC construits par les parties prenantes. Les composantes socio-économiques ont été modélisées par des sous- modules distribués dans un Modèle des Dynamiques des Systèmes Construit en Groupe (MDSCG). Chacun d’entre eux représente un secteur identifié par les intervenants, reproduisant les processus principaux suivants : pertes par infiltration, le stockage de surface, la quantité et la répartition de l’irrigation, l’extraction de l'eau souterraine, la pluviosité nette et le ruissellement, l’amélioration de l'efficacité de l'irrigation, la demande en eau agricole et, enfin, le revenu agricole. Des boucles de rétroaction entre les sous-modules distribués décrivent les interactions entre ceux- ci et permettent de simuler le comportement de l'ensemble du système à l'échelle du bassin versant. iv Les tests standards furent utilisés pour valider la structure du modèle et son comportement dynamique, bâtissant ainsi la confiance vis-à-vis des résultats. Les composantes physiques des DBC qualitatifs ont été modélisées avec SAHYSMOD (Modèle de salinité spatial agro-hydrologique). Le modèle distribué SAHYSMOD simule les changements des eaux souterraines, ainsi que le mouvement de l'eau et du sel dans la zone des racines des cultures à l'échelle du bassin versant. Le modèle a été calibré (1983-1988) et validé (1998-2003) sur des périodes de cinq ans en comparant le niveau des eaux souterraines observé avec le niveau simulé. Le modèle simule le niveau des eaux souterraines à un haut niveau de précision, avec un R2 de 0,906 et de 0,925; une efficacité Nash–Sutcliffe de 0,812 et de 0,873 ; et une erreur moyenne de 0,436 et de 0,486 pour les périodes d'étalonnage et de validation, respectivement. Les analyses d'incertitude et de sensibilité du modèle obtenues par GLUE (Estimation d’incertitude par
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