Utilization Efficiency Of Water Resources Research Articles

Water Planning and the Environment: 1776-1976

The history of the ways in which environmental factors have been integrated into water resources planning is divided into three periods. During the first period, the years from 1776 to 1900, there was relatively little concern over the environmental impacts of water projects. The second period, from 1900 to 1970, represents a period during which environmental issues were concerned largely with the elimination of recklessness and waste and the efficient utilization of water resources. Environmental factors sometimes received consideration as a result of the concerns of citizens' groups and as a result of interagency coordination requirements. The third period, the years since 1970, represents a time during which water resources agencies are routinely faced with a host of environmental concerns. Some of these relate to principal concerns of the previous period, i.e., the efficient use of resources. Others, e.g., the preservation of scarce natural environments and the maintenance of ecological stability and diversity, are relatively new issues.

Resistance‐energy Balance Method for Predicting Evapotranspiration: Determination of Boundary Layer Resistance and Evaluation of Error Effects1

AbstractAccurate estimates of evapotranspiration (ET) over large areas are needed for hydrologic studies, irrigation planning and scheduling, and other practices related to efficient utilization of water resources. One approach is the use of a resistance‐energy balance model of ET, the data for which can be supplied, in part, by remote sensing and in part from easily accessible records of National Weather Service observations. This model requires measurement of boundary layer resistance, crop and air temperature, net radiation, and soil heat flux. The objectives of this paper are i) to test the utility of the proposed model, ii) to determine boundary layer resistance at varying stages of crop growth, and iii) to evaluate the relative influence of errors in measurement of the meteorological and crop input parameters used.Measurements were made in fields of sorghum [Sorghum bicolor (L.) Moench] and millet (Panicum meliaceum L.) grown at Mead and Mitchell, Neb. Boundary layer resistance was estimated from friction velocity measurements used in a stability‐corrected aerodynamic method. Friction velocity was computed by means of the Deacon‐Swinbank approach. Evapotranspiration rates estimated by the resistance model compared well with results of lysimetric and energy balance measurements, on both a short‐period and a daily basis.The error analysis, in conjunction with field measurement, indicates that the resistance model evapotranspiration estimates are quite sensitive to errors in crop temperature measurement, especially in nonadvective conditions, but are less strongly affected by errors in the estimation of boundary layer resistance.

II. Representative view for the others

Identifying the drivers of species richness is a crucial for biodiversity conservation and community ecology. In this paper, the maximum utilization efficiency of water resources available to community is determined as the assembly law in an ecologically stable community with limited water resources. A plant community diversity model that incorporates water potential impedance is established, and the optimization model of community biodiversity structure was obtained based on water niche is also derived. It is shown that this optimization model can theoretically derive a species-area function similar to the traditional island biogeography curve, and it can also verify the predicted values of the species-area relationship experimentally and validated by long-term observations of plant diversity survey data. According to the model analyses, the total number of individuals (N) and the number of species (S) are determined by the combination of the water resources factors (the total quantity of available water resources in the growth season), the individual biological factors (the water consumption per unit mass of species in unit time), the complementary factors of inter- and intra-species water niche (the difference in water potential depending on the water use efficiency of the community), and plant community function factors (the total productivity of plant community). And as the area of plant communities increases, the heterogeneity of the water environment has increased. By adaptation and coevolution, more species are able to go through environmental and biological filtration, becoming community species that can utilize more available water resources at different spatial scales. Changes in water resources resulted in the community maximizing the utilization efficiency of water resources by adjusting the number and abundance of species. The main driving force for the increasing number of species is the full utilization of available water resources.

Heat Balance Climatological Method for Evaluating Supplementary Water Requirement to Paddy Fields

This paper describes an investigation into the supplementary requirements of water to the paddy field. The object has been to examnine the possibility of using the “HEAT BALANCE CLIMA-ATOLOGICAL METHOD” for evaluating the supplementary requirements of water.The results obtained from discussion in this paper may be summarized as follows:1. An estimate of the supplementary water requirements of paddy field, durinng the cultivating period, on an agroclimatological and hydrological basis would be of great value in the planning for efficient utilization of water resources. The following relations were derived, on the basis of water balance equation (1) in paddy field, as for the relations between the supplementary water requirements, the catchment area and the agroclimatic conditions:Pi*=ar*[Sw*/lr*{1+l(Pv*+Wt)/f·Sw*}-1], Ac/Af≅a/fr[Sw*/lr*{1+l(Pv*+Wt)/f·Sw*}-1]where Pi* is supplementary water requirement, Sw* net radiation over the water surface, r* rainfall, l latent heat of evaporation, Pv* seepage, Wt water required for harrowing the field, Ac is area of catchment, Af area of paddy field, f=0.85 is proportionality constant as shown in equation (7), a=0.8 is coefficient effective of rainfall, and fr is run-off coefficient.2. For evaluating Pi* and Ac/Af from the above relations, it is necessary to know the values and the seasonal variation of the net radiation Sw*. Figure 1 gives the comparison of the total short-wave radiation measured by the Robitzsh pyrheliograph with that estimated by the new empirical formula proposed by BUDYKO et al. Since a good agreement is obtained between these two, the new empirical formula was used to estimate the total short-wave radiation. The geographical distribution of the net radiation integrated for the cultivating periods (early culture, ordinary culture) is presented in Figure 2. The new amounts of net radiation exceed by about 10 per cent net radiation in the preceding papars (1959, 1962), but the relative geographical distribution of the net radiation does not show so much of a difference as compared with the foregoing.3. The comparison of the supplementary water requirements, as evaluated by the “HEAT BALANCE CLIMATOLOGICAL METHOD” and by actual measurement is shown in Figure 3. A substantial agreement is seen between these two. The main cause for the little discrepancy in the higher range of water requirements seems to be the disregard of the outflow of water from the paddy field in the “heat balance climatological method”. Such an agreement between them as shown in Figure 3, proves the heat balance climatological method for evaluating the supplementary water requirements of paddy field can be applied to practice.4. It is seen from Eqs (8) and (10 a), that the important quantities Pi* and Ac/Af in the investigation of water balance in paddy field and over wide area highly depend upon the non-dimensional parameter Sw*/lr*, which was adopted as one kind of agroclimatological indices and was known by the name of radiative dry index in the preceding paper (1962). Figure 2 shows the geographical distribution of radiative dry index derived from the data of net radiation and rainfall for the two cultivating periods. The agroclimatic condition in the early cultivation period is slightly dry in comparison with the condition in the ordinary cultivation period.

Industrial Waste Disposal Tailored to Stream Flow

Recognizing the technical and economic limitations of waste treatment in maintaining satisfactory stream conditions during drought season, two possibilities for more efficient utilization of water resources hold promise. Either the stream flow should be regulated to make a higher level of total flow usable; or the industrial waste discharge should be regulated, tailored to the varying pattern of stream flow. A detailed case analysis of the latter, regulating release from waste storage lagoons in accord with the varying waste assimilation capacity of the stream, indicates industrial expansion potential 10 to 50 times that possible under drought flow conditions.