Answer:
Introduction:
Mean precipitation over an area is an important parameter in hydrological studies and water resource management. It helps in understanding the average rainfall pattern and estimating the water availability in a particular region. There are various methods to obtain the mean precipitation, and among them, the orographically weighted isohyetal method is considered the best.

Orographically weighted isohyetal method:
The orographically weighted isohyetal method takes into account the influence of topography or mountainous features on precipitation distribution. It is based on the assumption that the amount of precipitation increases with altitude due to orographic lifting and adiabatic cooling. This method considers the elevation factor and assigns different weights to the precipitation values based on the elevation of the gauging stations.

Advantages of the orographically weighted isohyetal method:
1. Incorporates topographical influence: This method considers the orographic effect, which is particularly important in regions with significant mountainous features. It accounts for the fact that higher altitudes receive more rainfall due to the lifting of moist air.

2. More accurate representation: By assigning weights based on elevation, the orographically weighted isohyetal method provides a more accurate representation of the mean precipitation over an area. It considers the variations in rainfall patterns due to topography.

3. Better estimation of water availability: The orographically weighted isohyetal method helps in estimating the water availability in a region, which is crucial for water resource management. It provides a more realistic picture of the average rainfall distribution, considering the influence of topography.

4. Suitable for complex terrain: This method is particularly suitable for regions with complex terrain, where the precipitation pattern varies significantly with altitude. It can handle situations where other methods may not be able to capture the spatial variability accurately.

Conclusion:
The orographically weighted isohyetal method is considered the best for obtaining the mean precipitation over an area. It incorporates the influence of topography and provides a more accurate representation of the average rainfall distribution. This method is particularly useful in regions with significant mountainous features or complex terrain. By considering the elevation factor, it helps in estimating the water availability and is crucial for hydrological studies and water resource management.