Field deployment

On Monday the 24^th we departed Dakar and traveled to the Pont Gendarme field site for PSD deployment. In attendance: Makhfousse Sarr, Cheikh Toure, Madame Ndaiye, Adama, Anna, Marie, Madame Ndao. When we arrived in the afternoon we inspected the field sites with Abdoulaye Djiop to ensure access and inform him of our research and intent.

After scouting the sites we returned to Saint Louis for the evening. In the morning we left at dawn and traveled to the field site which is currently under rice cultivation. We met Abdoulaye Djiop and proceeded to deploy the PSDs at each sampling site. Each site received 4 cages with 2 PSD in each cage. A trip blank was kept in the glove compartment of one of the trucks in a sealed (clipped) Teflon bag. Staff collected water depth and cage depth (taken at the middle of the cages) measurements at each site. Mr. Djiop assisted greatly in the deployment at all sites. He ventured into the water, positioned the cages and took the depth measurements. I took photos with a digital camera, but the GPS unit’s batteries were dead so no coordinates were taken. We will try again on the first retrieval.

The first site sampled was the main drainage pumping station south of the fields. A field blank remained exposed for the duration of the deployment at this site. I presented a brief demonstration of proper handling and mounting of the PSD and then the staff continued on their own for the remaining cages. The PSDs were deployed after the pumping station for several reasons. In front of the station there was considerable activity the evening before by local residents playing in and collecting the water. Behind the station the area was secured by a locked gate providing security from tampering. Even though the pumps churn the water considerably when they are on, there was not any sediment due to the basin’s concrete lining.

Click on photos for larger image.

Positioning cages behind the main drainage pumping station.
Adama (left) and Mr. Djiop (right)

I had received reports of flooding in the area. Mr.Djiop informed us that the drainage pumping station removed the excess water from the canals. I observed cattle grazing to the west of the station.

I believe this location might be a good site for a meteorological station as it can be secured behind the locked gate and positioned well off the ground. Cons included the location near the pump building and proximity to a moderately traveled road.

The second site deployed was the primary irrigation canal located between the irrigation pumping station and the drainage pumping station. We took care to discretely position the cages and anchors to minimize their exposure. We observed local residents collecting household water from the canal. The water at this location was much more turbid than at the drainage pump station.

Loading PSD into cages
Left to right: Adama, Mdm. Ndao


Positioning cages in main irrigation canal.
Front to back: Mr. Djiop, Adama

The third site deployed was the primary irrigation pumping station (north). A local resident was seen fishing in the area. Water clarity was better than at the previous location, but this area is not lined with concrete. We attempted to minimize sediment disruption during deployment.

Greg Sower

Local fisherman at the main irrigation pumping station.
Cheikh (fore), Makhfousse

Loading PSD into cages.
Mdm. Ndao (front), Marie (L), and Anna

The PSDs were located ~3-4 m northwest of the canal and near the shore of the tributary. This was done to prevent interference with the boats and fisherman that use the canal mouth. The area was difficult to properly position the cages due to the extensive sediment and shallow approach.

Preparing to deploy cages at the irrigation pumping station.
Adama and Mr. Djiop

The final sampling site was the main drainage canal to the west. As in all previous locations the PSD cages were suspended from a rope spanning the canal. The staff positioned the anchors just above the water line and covered them with debris.

Positioning cages at the main drainage canal.

A water pumping station was located near this site and I was informed that it provided water to the tower located in a nearby village.

The complete deployment took approximately 1.5 hours and afterwards the remaining equipment was secured and we traveled back to Dakar.

While in Saint Louis I made phone contact with Tim Krupnik and we agreed to try to meet on Monday, October 1^st during our field retrieval.