Water supply monitoring of lake chad

Lake Chad

Lake chad is a large shallow lake bordered by the African countries of Cameroon, Chad, Niger, and Nigeria. The surrounding regions depend on lake chad as a primary source of fresh water and irrigation. This notebook will focus on monitoring the water supply in the Lake Chad region before and after the rainy season in 2015.


Orient Yourself with Lake Chad

The code below renders a map that can be used to orient yourself with the region. The Lake Chad region sustains several hundred small communities. See if you can spot any of them.


In [2]:
# Enable importing of utilities
import sys
sys.path.append('..')

## The code below renders a map that can be used to orient yourself with the region.
from utils.data_cube_utilities.dc_display_map import display_map
display_map(latitude = (12.2, 14.5), longitude = (12.9, 15.5))


Out[2]:


Lake Chad is shrinking

Over the last 40 years, Lake Chad has decreased by more than 90% in surface area from 26,000 sq. km to 1,500 square km.

This shrinkage has been a particularly popular case study due to the following factors:

  • the decline is large, and therefore easy to observe/monitor
  • weather/flooding patterns are predictable
  • the decline endangers many communities in the area. Studies on this region are important to mitigating the effects of a disappearing water supply.


Causes of shrinkage in Lake Chad

Possible causes of this shrinkage include:

Over-irrigation
to meet the needs of a growing population in the region. Irrigation demands increased four-fold between 1983 and 1994, accounting for 50 percent of the additional decrease in the size of the lake.

Climate change
A measured trend of dryer conditions. This brings about the need for more irrigation.

Declining Discharge
Discharge from the Chari/Logone river system has decreased in the last 40 years.


The infographic above was taken from the 2017 issue of Foresight Africa


Rainy Season

The climate in lake chad is fairly predictable. There is a rainy season that spans the summer months of June, July, and August. Followed by a dry season from September to May that sees little or no percipitation. This rainy season is the major source of water to Lake Chad.

Analyzing Lake Chad's surface area before and after the rainy season

Planning the analysis

This notebook is the first in a series of notebooks covering water-body analysis of Lake Chad. Specifically, we'll be looking at the effect that the rainy season has on the surface area of Lake Chad.

This analysis will require:

  • a means calculating when the rainy season starts and ends
  • a means of determining what part of the imagery is water
  • a means of determining how much water is in the lake
  • a comparison of before rain measurements to after rain measurements.

Datacube

The Datacube is an open-source data-aggregation framework for remote-sensing data. The following notebooks will show a detailed use for it.

Divide and conquer

To make certain concepts simpler to pick up, this water analysis task is split into smaller conceptually isolated pieces. Each receives a specialized treatment in a separate notebook. In order of analysis, the notebooks are as follows:


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