def _compute_basin_response_term(self, C, z2pt5):
        """
        Returns the basin response term (equation 12, page 146)
        """
        fsed = np.zeros_like(z2pt5, dtype=float)
        idx = z2pt5 < 1.0
        if np.any(idx):
            fsed[idx] = C['c11'] * (z2pt5[idx] - 1.0)

        idx = z2pt5 > 3.0
        if np.any(idx):
            fsed[idx] = (C['c12'] * C['k3'] * exp(-0.75)) *\
                (1.0 - np.exp(-0.25 * (z2pt5[idx] - 3.0)))
        return fsed
Returns the basin response term (equation 12, page 146)