|M.Sc Student||Gil Gutman|
|Subject||Mass Balance as a Key to Water Quality Management in Rivers|
Affected by Sea Water Entry
|Department||Department of Civil and Environmental Engineering||Supervisor||Professor Emeritus Galil Noah (Deceased)|
|Full Thesis text - in Hebrew|
Natural water bodies, among them streams and rivers, suffered over the years from severe pollution with many origins and sources. The natural water flows had been utilized and supplied for irrigation, drinking and other purposes. Now days, anthropogenic nutrients enrichment, especially with nitrogen and phosphorus, is one of the most serious pollution problems in rivers and the marine environment. Nutrients enrichment is the first step that may cause eutrophication conditions and chain processes starting with algal dominance changes, increasing biomass growth and decomposition, decreased light availability, reduced dissolved oxygen in the water column down to anoxic conditions, and harmful algae growth.
In order to prevent scenarios as mention above, there is a need to establish a water quality management strategy. Water quality management of natural water bodies consists on many elements and requires a 'whole system perspective' starting with environmental regulations, objectives and time tables, monitoring and documentation plans, pollutants limiting and enforcement acts, water utilization limitation and supplying, and maintenance acts, all these as a comprehensive managing interface. River water quality managing, especially in the downstream parts (estuaries) are complex due to the special hydraulic conditions and the interface between fresh water coming from the drainage basin and saline water coming from the sea, as well as biogeochemical processes taking place in the water column and the sediment.
Predicting and managing water quality of estuaries using complex conditions hydraulic model combined with water quality models, are usually based on mass balance approach. However, due to the system complexity and the internal processes taking place within it, there is a large use of process-based models using many assumptions and typical values of coefficients in order to quantify those processes. All this have a crucial influence on the degree of uncertainty and the accuracy of the out coming model prediction. The aim of the model is first to quantify the total maximum daily load (TMDL) that the ecosystem can tolerate without showing bad ecological responses. Further aim is to demonstrate scenarios and its responses, in order to make management decisions based on the model predictions.
This paper emphasis the role of internal processes in the mass balance performance and the necessity of examining the model suitability to the specific estuary characteristics, the availability of reliable data, and the degree of uncertainty that is expected, In order to adjust the theoretical needs and knowledge with the operative needs of the decision makers.