Sediment‐Related Transport of Nutrients from Southwestern Watersheds

Data from rainfall simulation experiments conducted in Arizona and New Mexico were used to identify relationships between total suspended sediment (TSS) concentrations (kg/ha/mm of runoff) in runoff and concentrations (kg/ha/mm of runoff) of total phosphorus (TP), total volatile suspended sediment (TVSS), and total nitrogen (TN). The units of kg/ha/mm of runoff are equivalent to mg/l divided by 100. Data were collected from pinyon‐juniper, ponderosa pine, short grass prairie, creosote bush, and bottomland vegetation types. Lumping data from these five vegetation types yielded a relationship for total phosphorus of $\mathrm{TP}=0.0013(\mathrm{TSS}{)}^{0.83}$ with a linear correlation coefficient of $r=0.77\text{.}$ The relationship for total volatile suspended sediment was $\mathrm{TVSS}=0.274(\mathrm{TSS}{)}^{0.72}$ $(r=0.91)\text{.}$ A poor relationship was found for total nitrogen with $\mathrm{TN}=0.008(\mathrm{TSS}{)}^{0.15}$ (with $r=0.11)\text{.}$ These relationships were validated using data from other rainfall simulation experiments and naturally occurring ephemeral streamflow in southern New Mexico.