An estuary is a partly enclosed coastal body of water with one or more rivers or streams flowing into it, and with a free connection to the open sea.
Estuaries form a transition zone between river environments and ocean environments and are subject to both marine influences, such as tides, waves, and the influx of saline water; and riverine influences, such as flows of fresh water and sediment. The inflow of both seawater and freshwater provide high levels of nutrients in both the water column and sediment, making estuaries among the most productive natural habitats in the world.
A more thorough definition of an estuary would be “a semi-enclosed body of water connected to the sea as far as the tidal limit or the salt intrusion limit and receiving freshwater runoff; however the freshwater inflow may not be perennial, the connection to the sea may be closed for part of the year and tidal influence may be negligible.”
This definition includes classical estuaries as well as fjords, lagoons, river mouths, and tidal creeks. Estuaries are a dynamic ecosystem with a connection with the open sea through which the seawater enters accordingly to the rhythm of the tides. The seawater entering the estuary is diluted by the freshwater flowing from rivers and streams. The pattern of dilution varies in different estuaries and is dependent on the volume of freshwater, tidal amplitude range, and the extent of evaporation from the water within the estuary. 
Nama sebenar Nurharyati Husna,nama kunyah Ummu Jauharah..Mahasiswi Usm,Penang..Major Biology Aquatik,minor Pengajian Islam,Arab bahasa Ketiga,tenang,selalu berusaha mencari,mempelajari dan mengamalkan kebenaran,berusaha untuk menjadi al-jama'ah yang dijanjikan nabi saw tanpa mengclaim diri sebagai al jama'ah,menghargai setiap muslim dengan keislamannya,setiap juru dakwah dengan kadar kebenaran yang dimiliki,namun tetap menebar amar makruh nahi mungkar.