| Intro |
Water storage dynamics in on-farm reservoirs (OFRs) are crucial for irrigation water allocation and utilization,
ensuring agricultural development sustainability. Previous studies have primarily relied on the area-storage
model to estimate reservoir water storage using meter-level remotely sensed data, which often falls short of
accurately capturing the water storage dynamics of OFRs, especially in small OFRs with steep slopes. Hence, we
proposed a method to estimate the water storage of OFRs in irrigation areas by integrating multispectral drone
data, high-resolution remote sensing data, and ground observations. The water surface area was extracted from
multispectral drone data using a Gaussian Mixture Model (GMM) and a threshold segmentation method. Slope
gradients were then obtained by identifying the maximum potential slope zone (PSZ) and utilizing highresolution
drone-based Digital Surface Models (DSMs). The dam slopes of the constructed boundaries were
automatically computed considering the significant decline of slope gradients. By combining the dam slopes of
the OFRs with water depth observations, we estimated the construction depth (H). Subsequently, current water
depth was obtained using drone-derived Digital Surface Models (DSMs), calculating the elevation difference
between drone-derived OFRs and water surface boundary. Once the OFR morphology was fully constructed, the
water storage was calculated based on area-storage and depth-storage methods using the 3D volume module in
Arcpy. The derived water storage agrees well with in situ observation (R2: 0.99) using slope gradients, reaching
an overall accuracy of 95.2 %, with a root mean square error (RMSE) and a mean absolute error (MAE) of
2785 m3 and 1820 m3, respectively. Notably, discernible fluctuations in water storage were observed during the
main irrigation phases, highlighting the essential role of OFRs in promoting equitable water resource distribution
and enhancing irrigation water management. This integrated approach offers a robust solution for monitoring
and managing water storage dynamics in agricultural areas. |
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