def _get_basin_response_term(self, C, z2pt5):
        """
        Returns the basin response term defined in equation 20
        """
        f_sed = np.zeros(len(z2pt5))
        idx = z2pt5 < 1.0
        f_sed[idx] = (C["c14"] + C["c15"] * float(self.CONSTS["SJ"])) *\
            (z2pt5[idx] - 1.0)
        idx = z2pt5 > 3.0
        f_sed[idx] = C["c16"] * C["k3"] * exp(-0.75) *\
            (1.0 - np.exp(-0.25 * (z2pt5[idx] - 3.0)))
        return f_sed
Returns the basin response term defined in equation 20