APPLICATION OF THE DEVELOPED (WQMIS) AS A DECISION SUPPORT TOOL FOR LAKE MANAGEMENT - Integrating GIS, Remote Sensing, and Mathematical Modelling for Surface Water Quality Management - page 191

9.1. DECISION SUPPORT FOR LAKE WATER MANAGEMENT
The developed WQMI includes a structured set of decision support tools for managing the watershed
such as the surface water quality geo-database, the 1D and 2D hydrodynamic models of the catchment
and lake system, the basic water quality modelling tool of the lake and the screening eutrophication
model of the lake. In this research study a main target was to create better understanding of the
complex water system and to provide useful and reliable knowledge for managing the watershed and
its components. The focus of the research was on the surface water quality management and
specifically the lake water system since it is the collector of all pollutants and wastes discharging from
the catchment. The main objectives of the DS tools are: The DSS will be an important tool to: to
increase the understanding of the relations between different users and the components of the water
system to integrate the different tools to overcome the lack of data and to provide a common and user-
friendly framework for the analysis and comparison of management options and measures though
using a set of physically based models supported by remote sensing data for calibration and validation
procedures. The developed set of water quality modelling tools is mainly focusing on prediction of
water quality concentrations and eutrophication indicators concentrations to assist in management of
the lake system. A plan for managing the water quality of the lake system can be implemented using
these models.
9.2. MANAGEMENT PREDICTION SCENARIOS FOR SHALLOW LAKE SYSTEM
The main function of the developed water quality and eutrophication modelling tools is to produce
predicted water quality concentrations for the assigned group of parameters specially the TSM and in
order to develop the possible management plans for lake pollution control and mitigation strategy. The
screening eutrophication model could be also used for predicting the CHL-a seasonal ranges for
management practices. As mentioned, discussed and concluded from this study, the main pollutants
entering the lake are from non point sources in the form of agricultural nutrients; mainly nitrogen and
phosphorous compounds, in addition to untreated wastewater that raise the concentrations of TSM. In
this research study a nutrient loads reduction methodology is presented, but for detailed and strategic
planning a wide range of temporal and spatial data sets will be needed.
As seen from chapter 5 the analysis results of the nutrients loads entering the lake shows amounts of
1080 ton/year of TP and 35x10 3 ton/year of TN. To reduce the pollutants loads to the lake and to
prevent more deterioration of lake water quality a set of planned scenarios for nutrients reduction is
developed and tested. The two main drains contributing to the lake pollution are Edko and Barseek
drains so the reduction of nutrients coming from these sources was investigated for pollution control.
The first set of developed scenarios involves equal reduction factors of nutrient loads coming from
both drains. The second set of scenarios involved only the reduction of pollutants coming from
Barseek drain which contributes by higher amounts of nutrients and wastes to the lake water,
(reduction factors from 0.05 to 0.5 were used in these scenarios).
It is also known that the aquatic vegetation biomass increases by the uptake of available phosphorus
and nitrogen from the water. It was found that the nutrient that will control the maximum amount of
plant biomass is the nutrient that reaches a minimum before other nutrients. Therefore, under certain
condition, nitrogen may reach a minimum value before phosphorus and, as a result, control the
maximum amount of plant biomass and vice versa. This situation depends on the relative amounts of
nitrogen and phosphorus required by aquatic plants and their availability in the water body.
Accordingly, a mass ratio of available forms of nitrogen and phosphorus (N/P) was used to calculate
the limiting nutrient in water. But from the modelling results this information could be also retrieved
based on the reduction scenarios that will be presented discussed below.