Lake Horo, or Lac Oro (18,900 ha) is located on The Inner Niger Delta in Northern Mali, it is separated from the river by a dam and a sluice gate. The Niger River is the longest river in West Africa and the third longest in Africa.

Delta topography is a complex mix of submerged lower areas and higher, unflooded areas known as tougérés. The floodplain consists of a vast network of river channels with leveés separated by low, clay-based floodplains.This natural depressions are filled once a year when the Niger River overflows.

Lake Horo is the only lake that has been developed for irrigation in Mali. In the bowl of Lake Horo, soil fertility is maintained by alluvial deposits of the Niger flood.

Prior to regulation, Lake Horo, contained at least some water throughout the dry season in years of good rainfall, but dried out completely by April in dry years. Now the sluice linking the lake with the Niger is opened in mid-November (earlier in years with poor rainfall) to all the lake to fill.

Floodplain recession agriculture is traditionally done along the banks of the major rivers, lakes and seasonal watercourses after the rainy season. In October-December flood recession enables sorghum and cowpea cultivation on floodplains, maize and sweet potato cultivation on exposed river banks using only soil moisture and harvest occurs on February-May. The funding window for this season goes from August to September.

OSM Mapping tags that I’m using:

• waterway=canal, service=irrigation => artificial waterways used for irrigation

• natural=wetland => area subject to inundation by water, or where waterlogged ground may be present

• seasonal=* => indicates if the wetland is seasonal

• natural=floodplain => floodplain is land adjacent to a stream or river that experiences occasional or periodic flooding

1 L’irrigation peut-elle se substituer aux cultures de décrue ?

2 fao: west-african-sahelian-floodplain

3 MALI: FLOOD MANAGEMENT - NIGER RIVER INLAND DELTA