Flow-Based Structural Modelling and Dynamic Simulation of Lake Water Levels

Introduction

Lakes are important reservoirs of large quantities of water and other resources of priceless value to society. Computer models have been crucial in understanding dynamic processes and their combined influence on large water bodies. Computer-based modelling and simulation under various assumed scenarios have been useful in the wider decision-making process for water resource management. To be useful for decision-making in this era, these models must have the expanded capability of accommodating multidisciplinary and multi-stakeholder inputs. Strategic policy and technical decisions can be better informed using simulations based on accurate data and sound mathematical relationships.

There is a need to understand and simulate the multiple scenarios that affect the water balance of large water bodies such as lakes, especially for strategic management and policy interventions. This becomes even more critical at this time when lake water levels are seriously affected by environmentally degrading human activities in their basins and global climate change. By providing the flexibility needed to construct and improve model structures as new knowledge becomes available in an interdisciplinary and multi-stakeholder setting, structural models can greatly add value to lake management decisions. The necessity to expand the hydroinformatics agenda by ensuring a more participatory process calls for a tool that can facilitate the exploration of the combined impact of the diverse factors and views influencing water management decisions in a transparent and versatile manner. The motivation of the moment is to transcend the usual black-box limitations of statistical analysis by using conceptual models to shed more light on the dynamic structural connections between the main system drivers within a given systems boundary.

This chapter uses a case study of Lake Victoria to demonstrate how a structural modelling approach with system diagrams showing dynamic interrelationships can improve the understanding and simulation of changes in lake water levels. The inflow and outflow processes, population growth, and accompanying state variables were modelled using STELLA, a dynamic modelling and simulation software system that has found many favourable applications to studies of complex dynamic systems. A brief background to the study highlights the main features of the study area and a review of the relevant literature. The methodology used to construct a conceptual model for the lake’s hydrological subsystem is described and the results got by simulating various assumed scenarios of water withdrawal and climatic variables are discussed. The chapter concludes with recommendations for improving the modelling approach to better support interdisciplinary research and holistic studies of the complex environmental problems facing lakes.