Abstract:
The effectiveness of watershed management practices on changing hydrological variables
like soil moisture content is not well explored in the scientific literature. Remote sensing is
an alternative data source to fill the gap of conventional methods for measuring soil
moisture. However, remote sensing products and techniques also need to be evaluated with
ground measurements. In this study, the impact of conservation measures on soil moisture
content was evaluated by integrating remote sensing with in situ soil moisture content
measurements. The approach started by measuring the soil moisture content using both
direct and indirect methods. Fifteen soil moisture content samples were collected from the
downstream, middle stream and upstream parts of the micro watershed. Additionally, the
corresponding measurements were conducted using the Delta T HH2 moisture meter. Then
the gravimetric method was used to calibrate the Delta T HH2 moisture meter. A uniform
sampling technique was used to collect soil moisture content measurements, used to
characterize its distribution by conventional methods. Therefore, this sampling technique
brought 57 sampling sites over the micro watershed. Next, these 57 samples were used to
spatially interpolate. An empirical (Multiple Regression Analysis) relation was established
for remote sensing-based soil moisture using 45 measurements for calibration and 15
measurements for validation. The soil moisture content was served as a dependent variable,
while the backscattering coefficient and local incidence angle of Sentinel 1A were served
as independent variables. The performance of the developed model showed different
accuracy at downstream, middle stream and upstream parts of the micro watershed with
R
2 = (0.32, 0.80 and 0.82), root mean square error (8.88 %, 6.26 % and 7.09%) and mean
absolute error (6.44 %, 5.0 % and 5.48 %), respectively. The result of this study showed
that the Sentinel 1A satellite can be used to estimate soil moisture content. Therefore, the
use of Sentinel 1A satellite product for soil moisture estimation is promising and hence
future planning, development and decisions can be based on it. The result from both direct
and indirect methods showed that the spatiotemporal dynamics of the soil moisture content
is highly affected by the rainfall event and topographic conditions. Moreover, the result
showed that there is a significant change in soil moisture due to the sustainable land
management interventions in Wutame micro watershed.
