Areal Coverages Research Articles

ESTIMATION OF PRE‐ AND POST‐DEVELOPMENT NONPOINT WATER QUALITY LOADINGS1

ABSTRACT: A simple procedure for estimating pre‐ and post‐development water quality loadings from residential communities is discussed. The procedure deals with: (a) gathering basic water quality loading numbers observed by others at several watersheds with various land uses; (b) obtaining the breakdown of proposed land uses at various phases of the community development; and (c) estimating pre‐ and post‐development water quality loading numbers by taking the weighted average of the basic loading numbers in terms of areal coverages of different land uses at various phases of development. Results of this simplified procedure have been verified indirectly by comparing them with the estimates derived independently through a more fundamental but time‐consuming approach.The procedure was used to evaluate the anticipated water quality impact of two future residential communities in South Florida by analyzing four water quality parameters: Suspended Soils (SS), Total Nitrogen (TN), Total Phosphorus (TP), and Biochemical Oxygen Demand (BOD5). Although computation of loading numbers with mixed land uses is not an exact science at the present time, the recommended approach appears to be the best available technique to analyze quantitatively the water quality‐quantity‐land use interactions.

On the Evaluation of Point Precipitation Probability Forecasts in Terms of Areal Coverage

Probability of precipitation (PoP) forecasts can often be interpreted as average point probability forecasts. Since the latter are equivalent to (unconditional) expected areal coverage forecasts, PoP forecasts can be evaluated in terms of observed areal coverages in those situations in which observations of precipitation occurrence are available from a network of points in the forecast area. The purpose of this paper is to describe a partition of the average Brier, or probability, score—a measure of the average accuracy of average point probability forecasts over the network of points of concern—that facilitates such an evaluation. The partition consists of two terms: 1) a term that represents the average squared error of the average point probability forecasts interpreted as areal coverage forecasts and 2) a term that represents the average variance of the observations of precipitation occurrence in the forecast area. The relative magnitudes of the terms in this partition are examined, and it is concluded (party on the basis of experimental data) that the variance term generally makes a significant contribution to the overall probability score. This result, together with the fact that the variance term does not depend on the forecasts, suggests that the squared error term (rather than the overall score) should be used to evaluate PoP forecasts in many situations. The basis for the interpretation of PoP forecasts as average point probability forecasts and some implications of the results presented in this paper for the evaluation of PoP forecasts are briefly discussed.

The Influence of Map Scale on Engineering Geologic Mapping

Various engineering geologic maps ranging from statewide to local site studies have been developed during the last decade in Missouri for land-use planning purposes. Because this work has been initiated at the request and with the support of various regional planning agencies, the scope and content of these maps has varied greatly. Several engineering geologic maps, considered most representative of mapping procedures used in Missouri have been compared with respect to cost (man-hours of effort), scope, mapping detail, definable mapping units and thoroughness of areal coverage; and application or potential use of the map by the non-geologist. Map scales vary from 1:24,000 to 1:250,000 and areal coverages range from 63 sq mi to 932 sq mi. The potential application or usefuluess of these maps has been evaluated in an attempt to determine a concept of cost to benefit ratios. No specific recommendations defining the “best” approach to this type of mapping can be made since each situation is unique. However, some guidelines and observations regarding the potential return for a given investment in engineering geologic mapping are presented.

The Ten-Pattern Steamflood, Kern River Field, California

The steamflood project at Kern River field consists of 10 inverted seven-spot injection patterns, with 32 producing wells covering 61 acres. Steam injection is confined to a 70-ft sand. Extensive data analyses confirm that steamflooding is a most efficient displacement mechanism, with a volumetric sweep of more than 60 percent. Introduction The 10-pattern steamflood field trial was initiated in the Kern River field, Calif., in Sept. 1968. This field was selected for a commercial test after the technical success of the steamflood process was confirmed by the Inglewood field test. The Kern River field properties of high oil viscosity, low reservoir pressure, shallow depth, and high oil saturation are all favorable for thermal recovery techniques. Chevron Oil Field Research Co. and Standard Oil Co. of California, Western Operations Inc., designed and operated the test to measure vertical and areal coverages, displacement efficiencies, and residual oil saturations with data from several temperature observation wells and core holes. This paper contains a description of the reservoir, the project facilities, and the performance to Oct. 1, 1973. project facilities, and the performance to Oct. 1, 1973. The project is analyzed in detail and the performance is compared with theory. Results of a new steamflood prediction method are also included. prediction method are also included. Project Description Project Description Field Area and Background The 10-pattern steamflood is being conducted in Section 3 of the Kern River field, near Bakersfield, Calif. The field was discovered in 1899 and was largely developed by 1915. The reservoir is 300 to 500 ft thick and is first encountered in Section 3 from 200 to 300 ft below the surface. The Kern River Sand Series productive limits are defined by the downdip China Grade productive limits are defined by the downdip China Grade Loop fault and by updip outcropping. The dip in Section 3 averages 3 degrees, and strike is on a northwest-southeast trend. The Kern River Sand Series consists of at least six sand bodies separated vertically by 6- to 20-ft-thick siltstone or clay intervals. A typical IES log of the Kern River Sand Series is shown in Fig. 1. The subject field trial is being conducted in the bottom sand interval, from 705 to 765 ft on the log. Upper sands will be processed successively from bottom to top. The productive intervals are friable and unconsolidated; the rock ranges from fine to coarse grain, poorly sorted sandstone, to conglomerate with pebbles from 1/4 to +5 in. in diameter. pebbles from 1/4 to +5 in. in diameter. The reservoir data, based on wells cored at the start of the project in 1968, are shown in Table 1. The average properties for the steamflood interval are 7,600 md properties for the steamflood interval are 7,600 md permeability 35 percent porosity, and an oil saturation permeability 35 percent porosity, and an oil saturation before steamflooding of 52 percent, equivalent to an oil content of 1,437 bbl/acre-ft. The steamflood project area is shown in Fig. 2. The project consists of 10 inverted seven-spot injection patterns covering 61 surface acres. The two central patterns are confined or backed up by the outside ring of injection wells and are the two key patterns for project analysis. The 6-acre patterns provided the project analysis. The 6-acre patterns provided the opportunity to evaluate the effects of patterns larger than the 2.5-acre Inglewood test. JPT P. 1505