River Estuaries

One example of God's supreme power is His creation of rivers and seas. Although  they mix  with one  another,  on one side  an individual  can drink sweet water and, a few meters  away, he can drink bitter  salty water. In spite of this, the sea never flows into the rivers. He explains this by saying that He erected a barrier between them so that one would not overwhelm the other. This phenomenon is now well understood.

“God is the one who caused two bodies of water to flow, one palpable and sweet,   the other salty and bitter. He placed   a barrier between them, a partition that they are forbidden to surmount.”   (Surah Al-Furqan, 25:53)

“He  causes  two bodies  of water to now  and  meet  together,  but between  them  is a barrier that they  cannot  surmount.”   (Surah Ar-Rahman, 55: 19-20)

“Or, who has made the earth firm to live in, made rivers in its midst, set on it   immovable mountains, and made a barrier between two bodies of flowing water?  (Can there be another) god beside God.  No, but most of them do not know.”  (Surah An-Naml, 27:61)

“Nor are the two bodies of flowing water alike, for one is palatable, sweet, and pleasant to drink, while the other is salty and bitter. Yet from each you eat fresh and tender meat and extract ornaments to wear. You see ships therein that sail through the waves that you may seek the bounty of God and be grateful.” (Surah Fatir, 35: 12)

Science only became aware of this phenomenon after the satellite Gemini 4 photographed the Nile Delta during 3-7 June 1965. The barrier between the river and the sea, which was described by God nearly fourteen centuries ago, is now known as estuarine circulation. The river transports three major types of material: fresh water, dissolved organic and inorganic substances, and such detritus as organic material, sand, silt, or clay (which helps to shape the coastline). Large rivers, such as the Nile, acquire a high speed during their journey toward the sea and, due to the resulting turbulence, carry a sizeable suspended load of clay, silt, and sand. The sudden change in velocity makes the sediment to drop out rapidly. Moreover, the colloidal clay fraction is coagulated by the salty water, which helps further sedimentation.

Most rivers debouch onto a continental shelf, which results in the formation of a delta that is usually located at the river's mouth. As fresh water flows into the ocean, it tends to ride over the denser salty sea water.

The two waters begin to mix, albeit slowly, as the fresh water goes further out into the sea. Since the river's water is added to the sea's surface, it tends to flow out slowly. To balance the loss of sea water due to river discharge on the surface, a supply of higher-density Sea water flows beneath the surface and toward the river mouth. This is known as estuarine circulation a process that consists of pushing sediment toward the continents to form, over time, deltas or build up the shoreline. This is how we understand the "barrier" God created between fresh water and sea water.

Most people do not realize that the creation of the heavens and the earth is greater than that of man (Surah Ar-Rahman, 55:57). He did not create "the heavens and the earth and what is between them to play" (Surah Al-Anbiya’, 21:16).  He knows their secrets (Surah Al-Furqan, 25:6), for they belong to Him (Surah Ta-Ha, 20:5-6). There is much to learn from the creation of the heavens and the earth, which is why God asked man to reflect on how all this has been made subservient to him (Surah Al-Baqarah, 2:164).

“Truly the creation of the heavens and the earth is a greater (matter) than the creation of mankind. But most of them do not understand.” (Surah Ghafir, 40:57)

“We did not create the heavens and the earth and all that is between them for (idle) sport.” (Surah Al-Anbiya’, 21:16)

Say: "The (Qur'an) was sent down by God, who knows the secret (that is) in the heavens and the earth. Truly, He is Oft­ Forgiving, Most Merciful.” (Surah Al-Furqan, 25:6)

 “(God) Most Gracious is firmly established on the throne (of authority). To Him belongs what is in the heavens and on the earth, as well as what is be­ tween them and beneath the soil.” (Surah Ta-Ha, 20:5-6)

 “Behold! In the creation of the heavens  and the earth, in the alternation of night  and day, in the sailing of ships through the  ocean  for  the  profit of mankind,   in   the  rain   that God sends from the skies and the life that He gives thereby to a dead earth, in the beasts of all kinds that He scatters throughout the earth, in the change  of the winds  and the clouds that trail them like slaves  between  the  sky  and the  earth (Here) indeed are signs for people  who  are wise.” (Surah Al-Baqarah, 2:164)