THE EFFECT OF TIDE AND RIVER DISCHARGE ON RESIDENCE TIME AT SEGARA ANAKAN LAGOON, CILACAP, CENTRAL JAVA

• Main Author: Agika Putra, Reza
• Format: Final Project
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/33092
• Institution: Institut Teknologi Bandung

The objective of this study is to learn the effect of tide and river discharge on residence time (RT) at Segara Anakan Lagoon with hydrodynamic and particle trajectory simulation using Delft3D-Flow Model. The verification of tidal elevation and discharge between data from model and observation are quite good. Two scenarios were made with differentiating the tide condition from the beginning of trajectory simulation (Scenario A: start from neap tide; Scenario B: start from spring tide) and the river discharge input to each scenario (Q0 = 220.47 ????3/????; Q1 = 220.47 ????3/????; Q2 = 164.53 ????3/????; Q3 = 82.79 ????3/????; and Q4 = 122.44 ????3/????). Generally, from the A and B scenario, the values of RT are increasing from the mouth of the lagoon (Plawangan Barat dan Plawangan Timur) to the middle of the lagoon. The result of two scenarios show that particle at the Zone 1 and 2 predominently exit the lagoon through Plawangan Barat, and particle at the Zone 3, 4, and 5 through Plawangan Timur. From the Scenario A and B, there are still particle left inside. The effect of discharge towards RT could be known with comparing the value of RT cause by variation of river discharge input conducted in Scenario A and B. At the two scenarios, RT with low value (Zone 1: 0.21 – 0.28 days; Zone 4: 11.46 – 14.16 days, and Zone 5: 5.15 – 7.57 days) occur when the input of river discharge is high (Q1 = 220,47 ????3/????), whereas RT with high value (Zone 1: 2.87 – 4.52 days; Zone 4: 26.36 – 30.04 days; and Zone 5: 14.17 – 20.45 days) occur when the input of river discharge is low (Q3 = 82,79 ????3/????). Different with other zone, at the Zone 2, the lowest RT is 6.48 – 10.41 days when the river discharge is low, whereas the highest RT (9.35 – 14.59 days) occur at the simulation with Q2 (164.53 ????3/????) as the river discharge. Meanwhile, at the Zone 3, the lowest RT is 16.66 – 17.22 days when the river discharge is high, whereas the highest RT (27.82 – 28.70 days) occur at the simulation with Q3 (82.79 ????3/????) as the river discharge. Moreover, the effect of tide condition during the first time of trajectory simulation could be known with comparing the value of RT at the Scenario A (start with neap tide) and Scenario B (spring tide). The value of RT at the Scenario A is longer than Scenario B with the difference of time at the Zone 1 is 0.39 days, Zone 2 (4.59 days), Zone 4 (3.20 days), and Zone 5 (3.91 days). Meanwhile, at the Zone 3, the value of RT at those two scenarios are not much different, with the difference only 0.84 days (3.60% from Scenario A).