Turkish President Recep Tayyip Erdogan is scheduled to meet US President Donald Trump in Washington next week.
The SDF said in a statement Tabqa would be turned over to a civilian council once fully secured.
"The combing operations are ongoing to ensure that the city is clear", said spokesman Talal Sello.
The city is a key waypost in the SDF's flagship offensive for Raqqa, the Syrian heart of ISIS's so-called caliphate, about 55 kilometres (34 miles) further down the Euphrates Valley.
The battle for Tabqa was marked by fears that fighting could damage the nearby dam - Syria's largest - with the potential for catastrophic flooding.
In Ankara, the deception vis-a-vis the US decision which came as high ranking Turkish officials such as the chief of the intelligence agency (MIT), Hakan Fidan, and the Chief of General Staff, General Hulusi Akar, were holding high level meetings in Washington to lobby against it, is very apparent in government circles.
The observatory also reported that casualties among civilians caused by airstrikes of the US-led coalition since the beginning of May 2017 rose to 59 persons.
Prime Minister Yildirim on Wednesday said the United States decision will "have consequences and will yield a negative result for the USA as well".
The U.S. announced Tuesday that it would arm Syrian Kurdish fighters as a necessary step to recapture the Islamic State stronghold of Raqqa despite opposition from Turkey, which views the group as an extension of the Kurdish insurgency in its southeast. "I hope they turn back from this mistake", Canikli said.
"I will personally express our worries in a detailed way when we talk with President Trump on May 16", he added, saying NATO's Brussels summit on May 25 would also tackle the issue.
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Until Tuesday, official United States policy was to supply weapons only to the Arab components of the SDF-never to its Kurds.
A first consignment of weapons is already in place for delivery and could be dispatched to the YPG "very quickly", U.S. Colonel John Dorrian said May 10.
The YPG has been seen by Washington as the best ally against militants in Syria.
Prime Minister Binali Yildirim said Wednesday, "You can not destroy a terrorist organization using another terrorist organization". It comes just as Turkey sent a high powered delegation to Washington to explain to the Americans Ankara's misgivings in detail.
"From our side, we want to keep good neighborly relations with Turkey", Redur Khalil said in a series of messages from Syria. "We've been conducting military and diplomatic dialogue with the Turks, and it was a very, very useful discussion today", Mattis said during a press conference with the Danish Minister of Defense.
Asked about U.S. pledges of support, Erdogan suggested he will seek further guarantees when he meets Trump.
During a visit to Montenegro on Wednesday, Turkish Foreign Minister Mevlut Cavusoglu said there was no difference between the Syrian Kurdish fighters and the outlawed Kurdish rebels fighting Turkey.
Arming the Kurds is the right tack for Trump to take, a decision that for months we have been urging both Trump and his predecessor, Barack Obama, to make. He said he had no details about the team's makeup.
But Turkey worries that advances by the YPG in northern Syria could enflame the PKK insurgency on its soil and that the weapons supplied to this militia will fall into PKK hands, like it happened in the past.