Laserfiche WebLink
<br />3 <br /> <br /> <br />002453 <br /> <br />In this paper the model is described, data needs for the model are <br />identified, methods used to extrapolate missing data needed by the model are <br />shown, model calibration is explained, and anticipated mining activity <br />provided by the Mined Land Reclamation Division is analyzed. These plans are <br />compared with the existing conditions from the calibrated model. The model <br />is to be used by the Division to help in the assessment of cumulative effects <br />of multiple coal mines in a drainage system. <br /> <br />Although the model is focused on the Trout Creek drainage, the State <br />also is interested in changes in dissolved solids resulting from m~n~ng <br />activity in Dry Creek (fig. 1). Insufficient water-quantity and water-quality <br />data are available from this drainage system for inclusion in the model. <br />Therefore, streamflow and dissolved solids were computed manually for Dry <br />Creek following the model algorithm. In this report, an analysis of Dry Creek <br />is given after the description of the model. <br /> <br />THE MODEL <br /> <br />The model, which routes streamflow and dissolved solids through the <br />stream network, was written by A. W. Burns (U.S. Geological Survey, written <br />commun., 1983) and has been used for other major stream systems in Colorado. <br />The algorithm is an accounting procedure that sums water quantity and quality <br />in monthly time steps from one or more upstream points to a downstream point. <br />The addition of water quantity and quality is done at individual points <br />called nodes. A reach is defined as the stream segment between nodes. In <br />the stream network examined in this report, there are 27 nodes. Data can be <br />entered, modified, or outputted at each node. Although the data are manipu- <br />lated at these nodes, the changes in quantity and chemical composition of the <br />water are attributed to the reach upstream from any particular node. As an <br />example, a simple stream network with a series of nodes is shown in figure 2. <br />If the concentration in dissolved solids is increased at node 5, this <br />increase is not necessarily due to a point source at node 5 but may be due to <br />diffused sources of increased salinity in the reach bounded by nodes 1 to 5 <br />and 4 to 5. <br /> <br />There are three kinds of nodes (fig. 2): input nodes, internal nodes, <br />and output nodes. Input nodes are the upstream nodes (nodes 1, 2, and 3 in <br />fig. 2) in the stream network. Because the summation process of water down- <br />stream starts at these nodes, the ideal case is to have streamflow-gaging <br />stations for the input nodes. This is not always possible, and some estimated <br />data must be used. <br /> <br />Water and dissolved solids from upstream nodes are accumulated by the <br />model at internal nodes (nodes 4, 5, and 6 in fig. 2). As such, some internal <br />nodes will not be shown in the stream network under analysis in this paper. <br />Internal nodes also are used to input proposed changes in water quantity and <br />quality at individual coal mines (fig. 1). These input changes at a node can <br />be point sources of water from dewatering activities or diffused sources of <br />water such as drainage from a coal spoil pile within the reach upstream from <br />the node. For brevity, there are instances when proposed changes of water <br />quantity and quality for several mines are combined at a single node. Thus, <br />there may not be an internal node for every mine in the watershed. <br />