The Saudi water management is mainly dams, but also a few wells. We found 2 out of 3 dams we planned to visit. The 2 locations we did not go for were Al-Khanaq (wrong side of Medinah for our itinerary) and Al Hasid (we thought we covered the TWHS enough after the second dam).

Sadd Samallaqi (close to Taif)
The dam is marked on google maps as Al Samallagi Ancient Dam. Just follow google and it will lead you right there. The road is paved, but there are no signs mentioning the dam. It about 200m long and up to 10m high. You can easily walk on top. Next to the dam you can find some old wells. A local shepherd was kind enough to show me one I missed. 

Sadd Al-Aqrab (close to Taif)
We failed on that one. It’s nowhere near a road, so we closed in offroad from the nearest road and started hiking. We were finally stopped by a river with a fence on the other side and gave up. At least we found some camels on the road.

Sadd Al-Bint (north of Medinah)
Just off road 15. There is even a brown sign announcing the dam. The dam is up to 30m high but collapsed after 135m. This dam is plastered on one side, giving it a special appearance. There is now a river flowing through, which makes it a very nice landscape. You can easily walk on top of the dam, but I would not go to the very end, as you can clearly see a big crack there.
We tried to drive to the bottom, but the road is not possible to drive without a pickup. So we simply climbed down, which is totally doable. 

These dams and wells were crucial in a country with very little water and the state of conversation (not “Arabicly” overdone) is also great. Clear yes from my side.