Sea Water Intrusion in Estuaries - Article Example

The results obtained using the model includes the measure of water level, discharge and salinity level. These have shown good agreement with the observed results. Also, a direct relationship between longitudinal salt dispersion with flood-ebb loop length and tidal efficiency is also confirmed in this study (Nguyen et al, 2008b). The prediction of the salinity distribution in the complex situations like multi-channel estuaries like Mekong delta have also been reported in the literature (Nguyen and Savenije, 2006).

Mekong delta is unique in its character. It has large number of branches and transports huge quantity of water (2000 cu.m per second) even during summer. The prediction model is framed on the principle that the multi-channel estuarine system would function as single entity and the paired branches could be appropriately combined to one. The results obtained from the analysis show that steady state models could predict the salinity levels very well. They could also explain the equilibrium conditions established in the estuaries during variable flow period especially during the dry seasons.

Also, authors have computed the system response time for Mekong also. The data used in the paper was collected during the period 1991 to 1998. As Mekong delta is a very active morphologically, it's topography too is undergoing continuous change due to the transport of sediments through the river. Hence, the model would require continuous improvement by incorporating the recent topographical details. Further, the model also has parameters like mean estuary depth and river discharge that have high degree of uncertainty (Nguyen and Savenije, 2006).

Determination of fresh water discharge is essential for quantification of salinity distribution. In the case of very low flows the salinity distribution is observed to be maximum. But the low fresh water flows coupled with high tidal flows make the accurate estimate of fresh water discharges very difficult. And in the case of Mekong delta, the multi channel characteristics make the accurate direct determination of discharge computation very cumbersome. A reliable model has been proposed to estimate the river discharge under the above situations (Nguyen et al, 2008a).

The principle applied in this process is the reverse calculation, from the known values of salinity distribution the authors have developed equations to determine the river discharge. In this connection, two separate approaches have been attempted for different clusters of rivers in this basin. In the first approach, based on the information on the salinity distribution and estuarine shape of each branch the discharge in the individual branches is computed. And in the other approach, from the combined shape of estuarine branches and the salinity distribution, the combined discharge is estimated.

These analytical models could be used to compute the river discharges in multi channel estuarine regions by collecting the salinity distributions (Nguyen et al, 2008a). ReferencesNguyen, A.D. and Savenije, H.H.G Salt intrusion in multi channel estuaries : a case study in Mekong delta, Vietnam, Hydrology and Earth System Sciences, 10, 2006, 743 -754.Nguyen, A.D., Savenije, H.H.G, Pham, D N and Tang, D T, Using salt intrusion measurements to determine the freshwater discharge distribution over