3. Results and discussion

#### 3.1. Hydrological and meteorological characteristics

Wind speed and rainfall pattern vary between the three lakes (Figure 3). Rainfall amount and wind speed in 2016 was highest in Durian Tunggal Lake compared to Bera and Bukit Merah lakes. Highest daily rainfall amount recorded was 151, 50, and 33 mm in Durian Tunggal, Bukit Merah, and Bera lakes, respectively. Wind speed was also highest in Durian Tunggal Lake followed by Bukit Merah and Bera lakes. Mean daily wind speeds were relatively higher in Durian Tunggal and Bukit Merah, namely 2.1 and 1.8 m/s compared to Bera Lake of 1.0 m/s. The highest daily mean wind speeds recorded in Durian Tunggal, Bukit Merah, and Bera Lake

The main rivers that flow into the Bukit Merah Lake are Kurau River and Merah River. Kurau River covers a large catchment with total surface area of 337 km2 and thus contributing bigger flow into the lake. Mean flow recorded at DID Pondok Tanjung monitoring station for the

the Tembagau River and Bera River, which channel backflow of water from Pahang River

inflows from tributaries are almost negligible for Durian Tunggal Lake. Durian Tunggal lake is more dependent on the inter-water transfer scheme from Muar River [16] consistent with qualitative observation. Generally, the small catchment and large conversion of forested land to agriculture in Durian Tunggal Basin are likely reducing the natural water resource supply within the catchment. In contrast, Bera Lake and Bukit Merah have large forest reserve and

In this chapter, evaluation of the model performance was based on the visual inspection of

east, north, and vertical directions was measured at one location in Bukit Merah using ADCP and used to calibrate the hydrodynamic model. The results show good agreement between measured and simulated velocities at 1-m depth (Figure 4a). However, proper agreement of velocities at different depths and water level was difficult to achieve due to many uncertainties connected with hydrology and water demand management. Additionally, temperature sensor was also deployed to calibrate the hydrodynamic model. Simulated temperature yields very good agreement with measured temperature (Figure 4b). Based on the coefficients of determi-

lation with the observed values at 1 m level. The coefficient of determination for temperature was 0.742. In Durian Tunggal and Bera Lake, temperature-depth profiling was carried out at few sites for calibration purposes. The coefficient of determination for temperature was 0.762

Hydrodynamic simulation in Bukit Merah Lake indicated that the major driving force of the hydrodynamic pattern in the reservoir is wind-driven motion. The hydrodynamic patterns at surface level as shown in Figure 5 were averaged from air-water interface to 0.5 m depth. The circulation pattern analyzed and modeled showed mixing and water movement in the lake, which is closely related to wind velocity and direction. For example, a northeast wind, with magnitude approximately greater than 3 m/s, can cause a substantial transport and circulation of water mass in Bukit Merah Lake. A much higher wind speed exceeding 7 m/s was recorded

) between model output and observed data, the simulated current has higher corre-

observed and simulated trends and correlation coefficients of determination (r

during monsoon season. Inflows from Bera River range between <1 and 12.2 m3

/s for Kurau River and Merah River, respectively [15]. The discharge of Kurau River

/s. Measurement recorded in 2012 showed flows of 26.7 and

Assessing the Hydrodynamic Pattern in Different Lakes of Malaysia

http://dx.doi.org/10.5772/intechopen.73274

/s. The main river that flows into Bera Lake is

2

). Flow field of

/s, while

77

were 7.8, 7.7, and 2.6 m/s, respectively.

based on measurement was approximately 13 m<sup>3</sup>

water catchment storage subsequently more inflows.

and 0.6 for Durian Tunggal and Bera Lake, respectively.

period 1960–2004 was 16.5 m3

3.2. Model calibration

nation (r

2

3.3. Model analysis

1.3 m<sup>3</sup>

Figure 3. Rainfall amount and wind speed in three lakes in 2016.

in Durian Tunggal and Bukit Merah, namely 2.1 and 1.8 m/s compared to Bera Lake of 1.0 m/s. The highest daily mean wind speeds recorded in Durian Tunggal, Bukit Merah, and Bera Lake were 7.8, 7.7, and 2.6 m/s, respectively.

The main rivers that flow into the Bukit Merah Lake are Kurau River and Merah River. Kurau River covers a large catchment with total surface area of 337 km2 and thus contributing bigger flow into the lake. Mean flow recorded at DID Pondok Tanjung monitoring station for the period 1960–2004 was 16.5 m3 /s. Measurement recorded in 2012 showed flows of 26.7 and 1.3 m<sup>3</sup> /s for Kurau River and Merah River, respectively [15]. The discharge of Kurau River based on measurement was approximately 13 m<sup>3</sup> /s. The main river that flows into Bera Lake is the Tembagau River and Bera River, which channel backflow of water from Pahang River during monsoon season. Inflows from Bera River range between <1 and 12.2 m3 /s, while inflows from tributaries are almost negligible for Durian Tunggal Lake. Durian Tunggal lake is more dependent on the inter-water transfer scheme from Muar River [16] consistent with qualitative observation. Generally, the small catchment and large conversion of forested land to agriculture in Durian Tunggal Basin are likely reducing the natural water resource supply within the catchment. In contrast, Bera Lake and Bukit Merah have large forest reserve and water catchment storage subsequently more inflows.
