Modeling the effect of snow on seasonal runoff within the Truckee River drainage basin

EXTRACT (SEE PDF FOR FULL ABSTRACT): We estimate monthly runoff for a 2-dimensional solution domain containing those areas tributary to Pyramid Lake, Nevada (the Truckee River drainage basin) at a 1-kilometer grid cell spacing. ... To calculate the effect of snow on the hydrologic system, we perform two experiments. In the first we assume that all precipitation falls as rain; in the second we assume that some precipitation falls as snow, thus available water is a combination of rain and snowmelt. We find that considering the effect of snow results in a more accurate representation of mean monthly flow rates, in particular the peak flow during the melt season in the Sierra Nevada. These preliminary results indicate that a relatively simple snow model can improve the representation of Truckee River basin hydrology, significantly reducing errors in modeled seasonal runoff.

River salinity variations in response to discharge: examples from the western United States during the early 1900s

Major controls on river salinity (total dissolved solids) in the western United States are climate, geology, and human activity. Climate, in general, influences soil-river salinity via salt-balance variations. When climate becomes wetter, river discharge increases and soil-river salinity decreases; when climate becomes drier river discharge decreases and soil-river salinity increases. This study characterizes the river salinity response to discharge using statistical-dynamic methods. An exploratory analysis of river salinity, using early 1900s water quality surveys in the western United States, shows much river salinity variability is in response to storm and annual discharge. Presumably this is because river discharge is largely supported by surface flow.

Disturbance climate in the Columbia River Basin [abstract]

EXTRACT (SEE PDF FOR FULL ABSTRACT): Climatological events that disturb a landscape are important components in ecosystem processes. Modern ecosystem management plans now hope to incorporate knowledge of the spatial distribution and frequency of disturbance climate. The following describes a few analytic tools developed to help managers include disturbance climate in an ecosystem management plan for areas in the Columbia River Basin of the northwestern United States.

An uncommon period of cold and change of lapse rate in the Rocky Mountains of Colorado and Wyoming

EXTRACT (SEE PDF FOR FULL ABSTRACT): Temperature and lapse rate show extreme departures from mean values for May 1981 through October 1986 at the high-elevation station D1 on Niwot Ridge in the Front Range, Colorado. If the D1 record is accurate, this period may present an opportunity to identify factors that influence temperature at high elevations, but not necessarily at low elevations. This paper focuses on four questions: (1) Is the D1 temperature record accurate? (2) What is the geographical extent of this anomalous cold period? (3) Are there any identifiable contributing factors or physical events relating to this period? (4) Is there evidence of a similar anomalous period in the past?

Monte Carlo simulation of streamflow of the Salt River, Arizona

EXTRACT (SEE PDF FOR FULL ABSTRACT): Evaluations of the impact of climate change (such as a greenhouse effect) upon water resources should represent both the expected change and the uncertainty in that expectation. Since water resources such as streamflow and reservoir levels depend on a variety of factors, each of which is subject to significant uncertainty, it is desirable to formulate methods of representing that uncertainty in the forcing factors and from this determine the uncertainty in the response variables of interest. We report here progress in the representation of the uncertainty in climate upon the uncertainty in the estimated hydrologic response.

Food and feeding habits of Schizothorax longipinnis Heckel from River Jhelum, Kashmir

Food and feeding habits of Schizothorax longipinnis inhabiting river Jhelum were studied by observing the gut contents of 225 fishes. The species is found to be illiophagic and herbivore in nature, chiefly feeding on decayed organic matter (54.2%), sand and mud (25.7%), food of plant and animal origin (20.1%). Correlation between food intake and various size groups for different seasons have been discussed in details.

Preliminary observations on the availability of Tor tor (Hamilton) fry in the River Narmada near Hoshangabad, Madhya Pradesh

Collection of mahseer (Tor tor) fry during December to January from three centres of the river Narmada near Hoshangabad, (Joshipur ghat, Dungerwada ghat and Kherra ghat) using a special type of fry collection net is described. The physical features and physico-chemical conditions of the collection sites are also dealt with.

Note on the occurrence of minnows in the gut of Schizothorax longipinnis Heckel from River Jhelum, Kashmir

The carnivorous feeding behavior of some adults of Schizothorax longipinnis Heckel was observed during 1979-81 and the details are presented in this communication.

The age and growth of catfish Rita rita (Ham.) from the River Yamuna in north India

The age of 224 fishes was determined by counting the translucent zone on the opercular bones and otoliths. Back calculated annual growth of the fish revealed that the absolute growth of the female was better than that of the male upto the third year. From the fourth year onwards the growth of the male exceeded the growth of the female.

Seasonal variation and species diversity of fishes in the Neyyar River of the Western Ghats

Temporal variation in the abundance of fish populations and diversity of assemblages in different sections of the Neyyar River in the Western Ghats were investigated during the year 1984. A decreasing trend in the abundance of fishes from the headwaters downwards has been noted. The fish community is represented by 33 species assignable to 15 families. The diversity indices of Shannon-Wiener and Margalef and Pielou's evenness have been calculated. The diversity indices are discussed in the light of species richness in different sectors.

Organic carbon in the sediments of the lower reaches of Periar River

Sediments are indicators of the quality of water overlying them and hence, useful in the assessment of environmental pollution. Temporal and spatial variations in sediment characteristics and organic carbon content from 9 stations in the lower reaches of Periyar River an area in Cochin Backwater, India which is polluted from different sources were studied for one year during 1981. Variations in colour and texture of sediments were brought about by changes in the grain size and state of oxidation of organic matter. The colour of the sediment varied from greyish black at stations 1 and 2, brownish at station 3, black at stations 4 to 8 and reddish at station 9. Organic carbon and sediment texture showed a direct relationship at all stations except at station 9 where organic carbon content showed an irregular pattern. Overall range of organic carbon content was between 1.19 and 29.6 mg.g super(-1). The mean organic carbon of the stations ranged between 6.8 mg.g super(-1) (station 5) and 20.8 mg.g super(-1) (station 9). On the whole temporal variations were considerable with high values at station 9 and low values at station 5. Fluctuations were more at stations 6, 7 and 8.

The marked reduction of the Indus river flow downstream from the Kotry barrage: can the mangrove ecosystems of Pakistan survive in the resulting hypersaline environment?

This report deals with the application of knowledge of mangrove ecosystems from around the world to the understanding of the present status of mangroves ecosystems in Pakistan.

Fishing gear and methods of the river Brahmaputra in Assam

Potentially the inland fishery resources of the country are of very high order. But the present level of their exploitation is far from optimum, mainly because of the inadequacies of the existing fishing gear and methods. There is vast scope for increasing the fish production from inland waters by improving the existing gear and methods. This would require a thorough study of the fishing gear and methods in vogue, of which very little is known at present. In the present communication the authors discuss the fishing gear and methods of the river Brahmaputra, in Assam, based on a survey carried out by them during January-February 1964. The survey covers a 640 km stretch of the Brahmaputra River, its important tributaries and connected bheels, from Dhubri to Dibrugarh. As a result of the survey about 19 types of fishing nets, which could be grouped into eight classes, were identified. The salient technological features of the gears and their methods of operation are discussed class-wise. The characteristics of the individual types are shown in tables. The materials used for gear and gear accessories, are briefly discussed. The classification and relative importance of different types of gear are examined. Besides, the influence of the ecological and topographical features of the river on the development of different types of fishing gears, is also discussed.

Estimation of maximum sustainable yield (MSY) of hilsa (Tenualosa ilisha Ham.) in the Meghna river of Bangladesh

MSY per recruit of Tenualosa ilisha in the Meghna river was predicted as 112 g per recruit at the F(msy)=0.6/yr and at T(c)=0.6/yr. But Y/R=95 g per recruit was obtained at the existing fishing level, F=1.14/yr and at T(c)=0.6/yr. Existing F level was nearly double than the F(msy) level. Fishing pressure should be reduced immediately from F=1.14/yr to F(msy)=0.6/yr. F(msy)=1.14/yr was the same at first capture, T(c)=1.0, 1.2 and 1.4/yr, and MSY could be obtained as 142 g, 162 g and 176 g per recruit respectively. It is easier to change the first capture age (Tc) rather than changing off level. So, hilsa fishery manager may adopt F(msy)=1.14/yr while age at first capture must be increased from T(c)=0.6/yr (3 cm size group) to T(c)=1.4/yr (25 cm size group), by which 1.8 times production could be increased than the present production. MSY also possible to obtain as 201 g and 210 g per recruit at F(msy)=2.0/yr and 4.0/yr at T(c)=1.7/yr and 1.9/yr respectively. Under both the situations, hilsa production could be increased 2 times than the present production. To obtain the MSY=210 g per recruit the fishing level could be increased up to F=4.0/yr at T(c)=1.9/yr (34 cm size group). Economic point of view, hilsa fishery managers may choose to obtain the economic MSY as 201 g per recruit at F(msy)=2.0/yr and T(c)=1.7yr (31 cm size group) in the Meghna river of Bangladesh.