Annea knows about a water source on Elaaden. Rather than share its location, she sells water to the planet's inhabitants, who then live and die by her whim. Looking into this situation would probably benefit all involved, as well as Elaaden's future residents.
This mission can be acquired at the Flophouse on Elaaden. Just outside the cave entrance where Search for the Stolen Remnant Drive Core concludes, you'll see a lookout tower, with a "new mission" marker on the map. As you approach the tower, you'll hear comm chatter between a couple of scavengers. It's coming from a console on the platform at the top of the tower. Jump up there and interact with the console to activate the mission.
Go to the Paradise Edit
This is where you landed on Elaaden for the first time. You've likely already been in the Paradise, which is Annea's shop, and the nearby Paradise Sands forward station should have been deployed by now.
Find Annea's office Edit
Annea's office is right above her shop. You'll discover that the door is locked, but scanning reveals a conduit leading down through the shop.
Scan for a network console Edit
Follow the conduit until you find a console. It's not exactly hidden, but it is behind a platform.
Hack the network console to access Annea's office Edit
Using the console gives you a passcode for Annea's office door
Enter Annea's office Edit
Do as it says. (The game's journal writers really hold your hand for this mission.)
Search for clues about the location of the water source EditInside the office you'll find a datapaf:
You now have a new navpoint on your map.
Go to the water source Edit
The nav point leads you to a door in a rock outcropping in the eastern dunes; it's a sort of oasis, and the trees around the outcropping should make it easy to spot. (Note that this door will be locked until you progress the mission to this point.) Inside the door you'll find a cave, with glowing fungi and a pipe system leading inward.
Scan for information Edit
Follow the pipe into the cave. Soon you reach an underground lake. At the end of a pier extending into the lake you'll see a Remnant device; apparently this lake is a Remnant creation too. Scan the device. A few seconds later a cutscene begins, as Annea arrives with her guards.
Talk to Annea Edit
Annea's not very happy with Ryder, who she thinks is trying to ruin her livelihood. She reveals that her brother, Asgaar, had given out water freely, only to be killed for the water by scavengers. After that Annea decided to use her control over the water supply for power and security instead. She wants to continue this arrangement; she's willing to sell water to the krogan and the outpost, as before, and will offer Ryder a cut of the business. Ryder can accept this deal or reject it.
If the deal is accepted, Annea and her guards depart.
If the deal is rejected, Annea will use her bioelectricity as a distraction and run off, leaving her guards -- 4 Raiders -- to fight Ryder and company. They should be easy enough to kill as long as you get Ryder into cover quickly. After they're dead, Ryder contacts the Nexus to request new management for Annea's business.
Return to the Paradise Edit
The final step is to return to the Paradise and talk to whoever's in charge there. If Annea has run off, Addison and Kesh have sent Nexus staff. Otherwise, Annea's back in her shop, and reminds Ryder that she left a container of goods for him in her office upstairs.
530 XP, plus additional combat XP if Annea's guards are killed.
If Annea's deal is taken, the contents of the container seem to be fixed as 1 Sidewinder IV, 25 Omni-Gel Canisters, and 1 Shield Focusing Module.
If Annea ran away, she can be found later in a camp in Gehenna Valley, in a valley south-southeast and over the ridgeline from the forward station. If Ryder talks to her, she'll have decided that the Roekaar are right, and she and her guards (2 Adhi, 2 Scavengers) then attempt to kill Ryder.