Hi Shaimaa,

When conducting geostatistical analysis for water quality, the selection of the distance between points in canals and lakes depends on your specific research goals, but there are three general approaches you can follow:

Regarding the number of points, it is essential to collect at least 30 points for statistical robustness. However, the exact number can vary based on the size and variability of the area being studied.

As for the distance between points, it depends on the nature of the study. For instance, if you're comparing your water quality points with satellite imagery, the distance between points should be large enough to avoid multiple points falling within the same pixel.

In another example, if you're collecting depth data, the distance between points should be adjusted according to the seabed's topography. If the seabed is steep or irregular, shorter distances between points may be necessary to capture changes accurately. In contrast, if the seabed is relatively flat, larger distances might be appropriate.

You might find this reference is helpful

Field and Laboratory Methods for General Ecology: Brower, James E., Zar, Jerrold H., Ende, Carl Von: ISBN-13: 9780697243584

I hope this explanation helps!