To begin with, we will answer the question, then examine the answer. Genesis 7:11 tells us that "on that day all the springs of the deep burst forth, and the floodgates of the heavens were opened. And rain fell on the earth forty days and forty nights." Now that we know the source of the water - the "fountains of the great deep" (also known as springs of the deep) and the "windows of heaven" (also known as the floodgates of heaven), what exactly are these sources?
The fountains of the great deep is used only in Genesis 7:11, but the "fountains of the deep" is mentioned in Genesis 8:2, clearly referring to the same source, "Now the springs of the deep and the floodgates of the heavens had been closed, and the rain had stopped falling from the sky." The phrase "the great deep" is used three times in Scripture, in Isaiah 51:10, referring to the ocean, Amos 7:4, referring to God's fire of judgment drying up the oceans, and again in Psalm 36:6 where the phrase is used metaphorically of God's judgment and justice.
The phrase, "the deep," is use frequently, usually referring to the oceans (Genesis 1:2; Job 38:30, 41:32; Psalm 42:7, 104:6; Isaiah 51:10, 63:13; Ezekiel 26:19; and Jonah 2:3), though sometimes the phrase is indicating subterranean water sources (Ezekiel 31:4, 15) We also find that the Hebrew word mayan is translated as "fountains," which means, "fountain, spring, or well."
Many Young Earth Creationists agree that the fountains of the great deep are more than likely oceanic or subterranean sources of water, or, in the context of a worldwide flood, probably both. Since the fountains were a source of water, it must have been a major source. Answers In Genesis gives the following explanation:
"Genesis 7:11 says that on the day the flood began, there was a 'breaking up' of the fountains, which implies a release of the water, possibly through large fissures in the ground or in the sea floor. The waters that had been held back burst forth with catastrophic consequences. There are many volcanic rocks interspersed between the fossil layers in the rock record - layers that were obviously deposited during Noah's flood. So it is quite plausible that these fountains of the great deep involved a series of volcanic eruptions with prodigious amounts of water bursting up through the ground. It is interesting that 70 percent or more of what comes out of volcanoes today is water, often in the form of steam."
"In their catastrophic plate tectonics model for the flood, Austin et. al. [other authors] have proposed that at the onset of the flood, the ocean floor rapidly lifted up to 6,500 feet (2,000 meters) due to an increase in temperature as horizontal movement of the tectonics plates accelerated. This would spill the seawater onto the land and cause massive flooding - perhaps what is aptly described as the breaking up of the "fountains of the great deep. During the Flood, the world was deluged in 40 days of rain. But this was not the major source of the Flood waters."
As aforementioned, the other source of the floodwaters was the "windows" (or floodgates) "of heaven." Genesis 7:12 tells us that it rained for 40 days and nights non-stop. Now, Genesis 2:5 tells us that before man was created, there was no rain, and that Eden is watered from underground springs. It is because of this that many have developed the Water Vapor Canopy, which we will examine later on, a theory in which I used to believe.
Some people even believe that there were no rainbows before the Flood - and in turn, no clouds, nor rain, before the Global Flood. Consider the following: if clouds and rainbows did not exist before the Flood (in what is sometimes called the Antediluvian), why would it make a difference, since, a little over 2000 years later, Jesus used win (which was pre-existing) to establish the New Covenant with man. (See entry: "Covenants: The Old and The New")
As many scientists point out, a pre-flood hydrologic cycle without clouds and therefore without rain is difficult to fathom, as the sun's heat would have evaporated large amounts of surface water which would in turn eventually condense back into water. (In its liquid state) These droplets of liquid water form clouds - the source of rain.
Now, just like with the "great deep," the "windows of heaven" is found elsewhere in Scripture aside from Genesis 7:11 and 8:2. We find it in 2nd Kings 7:2 and 19, referring to God's intervention in regards to sending rain, and in Malachi 3:10, in reference to God pouring out blessings upon his people. In other words, the windows of heaven were not ordinary rain - the phrase is used to indicate the powerful and extraordinary nature of the rainfall.
Let us continue by examining the water vapor canopy theory. Genesis 1:6-8 tells us that on the Second Day of creation week, God "made the vault [firmament] and separated the water under the vault from the water under it. God made the "firmament" between these waters. Many people believe the firmament, or "expanse" (Hebrew, raqiya) separating the atmosphere - where birds fly - from a layer - a water vapor canopy surrounding the Earth.
However, when we read Genesis 1:20, "let the birds fly above the ground across the face of the expanse of the heavens," this allows for a bit more. In his book, A Biblical Basis for Creationists Cosmology, Dr. Russell Humphreys argues that since Genesis 1:17 tells us that God put the sun, moon ("He made also the stars") in the "expanse of the heaven" that the expanse must include interstellar space, therefore placing the waters above the expanse of Genesis 1:7 beyond the stars - at the very edge of the universe.
Many place emphasis on these "waters above." As stated, some believe the waters to be a water vapor canopy that once enveloped the Earth. The theory is so attractive because it can account for a canopy that shielded the pre-Flood people from radiation that allowed them to live longer and have better food. Dr. Larry Vardiman, after doing research into this theory, modified the theory to suggest that the "waters above" could have been small particles of ice that were "distributed in equatorial rings around the earth similar to those around Venus."
The general concept is as follows: the floodgates of heaven being opened are believed to be the collapse of the canopy upon the earth, due to volcanic eruptions from the breaking up of the fountains of the great deep that threw dust into the canopy and caused the vapor to nucleate and make rain. The coal seams found in Antarctica that contain vegetation found growing at the poles that seemingly grew under warmer conditions have been taken as evidence for this concept.
However, as attracting as this theory sounds, there is a very large problem which is too big to ignore. If there was such a water vapor canopy, the Earth would become superheated and unbearable hot and unsuitable for life. We do find evidence of volcanic and seismic activity during the Flood, yes, but if there truly was a Water Vapor Canopy, the years between Creation and the Flood would have to be accounted for using this model.
Vardiman and many others attempted to find a solution to this, having to very drastically reduce the amount of water vapor in the canopy from 40 feet to 20 inches. This would not be able to contribute to the forty days and nights of rain at the beginning of the Global Flood. S. A. Austin using the catastrophic plate tectonics model for the Flood, finds volcanic activity, which is associate with the breaking up of the ocean floor at the start of the flood - would have formed a linear geyser of superheated steam from the ocean... which would have caused very intense rain on a global scale.
If there was a water vapor canopy holding more than two meters, which is seven feet, of rain would have superheated the earth, and since the problem cannot be conclusively solved, the model is abandoned in light of the catastrophic plate tectonics model, which certainly accounts for the chaos caused during the flood - evidenced by what we find all around us today.
For example, Psalm 104:7-8 describes what occurred to the waters - as well as the earth's crust, "But at your rebuke the waters fled, at the sound of your thunder they took to flight; they flowed over the mountains, they went into the valleys, to the place you assigned for them." Geologic evidence shows us that the evenness of the Earth shifted, and valleys went down as mountains shot up.
Think of it a bit like a water bed - if someone jumps on one end, the person lying on the other will "shoot up." In the same way, the ocean floor was covered with fossils during the flood due to the catastrophic conditions, and when the mountains shot up, having been on the ocean floor, it took the fossils with them, thus the reason we find fossils of seashells at the top of Mt. Everest and whale fossils at the Andes Mountains, among other such things.
We see scarring left over from the flood over the world. We find fossils rapidly buried, buckled mountain ranges, even-places such as the Abyssal Plain, mountains "shaved," as if powerful waves swept across the forming mountains when they were soft, among many other such things. When the waters continued to recede from the flood, it caused massive sheets of water to race across all of the continents and "shave" the tops off of some mountains.
We also find evidence of rapid sanding. For example, sand grains in Northern Arizona have been discovered to have come from Pennsylvania, New York, and even farther north, in Canada. How could these grains have been transported 1,250 miles the length of the United States? A Global Flood. As discussed an a past entry, the Mid-Atlantic Ridge was part of the fountains of the great deep bursting forth - even to this day is still spews out lava and water.
If the floodwaters were enough to cover the mountains and the entire earth, would we not still find evidence of this water? Indeed we do. Take for example what Scientists have deemed "the blob." Beneath the Earth's mantle located about 500 miles underneath the Caribbean Sea a"blob" of water has been found - 80 miles thick and 380 miles tall. The Ogallala Aquifer is another example. It is an underground water source so large that it lies beneath eight states in the Unites States - and occupies roughly 175,000 sq. miles. An underground ocean about the size of the Artic ocean has been discovered in the Earth's mantle.
Another interesting find is the Wadsleyite Deposit. It has been found that below the Earth's mantle is a mineral called Wadsleyite, which holds large amounts of water. There is so much Wadsleyite that is has been estimated that it all holds enough to fill 10-30 of our oceans. It sounds as if there is plenty of water. Genesis 8:3 tells us, "The water receded steadily from the earth." The water is still on the earth, in fact it is all around us, we only need to investigate to discover it.
Simply put, the waters from the Flood were likely the bursting of underwater springs and volcanic activity (along with seismic) which lead to global catastrophe. (To understand how the Ice Age fits in with the Flood, see entry, "Is The Ice Age Biblical?") Thank you for taking the time to read this entry of, "The Truth." Please feel free to email me at email@example.com or the ministry team at firstname.lastname@example.org, comment below (please remain civil in your comments), visit the facebook page, or visit the Ministry homepage. Take care, and may God bless. Troy Hillman
 Strong's Concordance
 "Noah's Flood - Where did the water come from?" Web. 15 Dec 2010. http://www.answersingenesis.org/home/area/tools/flood-waters.asp
 L. Vardiman. The Sky Has Fallen. Pro. First ICC, 1986. 1:113-119
 Ibid. 
 "A Judged Creation." Web. 28 Dec 2010. http://www.getalifemedia.com/