16range^5\)</p></li>
<li><p>gaussian: \(2 exp(-r^2) * (1 - pnorm(r * 2^{1/2})) * W\)</p></li>
<li><p>none: \(I\) * W</p></li>
</ul><p>Details describing the <code>F</code> matrix in the <code>epa</code> covariance are given in Garreta et al. (2010).
Flow-unconnected elements of \(R(zu)\) are assumed uncorrelated.
Observations on different networks are also assumed uncorrelated.</p>
<p><code>taildown_type</code> Details: Let \(D\) be a matrix of hydrologic distances,
\(r = D / range\),
and \(I\) be an identi