dt>
<dd><p>Numeric value indicating the month (<code>1</code> through <code>12</code>) of the start of water year for
analysis. Default <code>1</code>.</p></dd>


<dt>start_year</dt>
<dd><p>Numeric value of the first year to consider for analysis. Leave blank or set well before start date (i.e.
<code>1800</code>) to use from the first year of the source data.</p></dd>


<dt>end_year</dt>
<dd><p>Numeric value of the last year to consider for analysis. Leave blank or set well after end date (i.e.
<code>2100</