When two rivers meet, how we decide which is main river and which is tributery? What are the criterion to decide this?

Hi all,

I have a question regarding the relationship between evaporation and groundwater fluctuations. Does evaporation cause groundwater to fall, or does rising groundwater lead to increased evaporation?

By "evaporation," I mean actual evapotranspiration from the land surface, as defined by most evapotranspiration models (e.g., GLEAM, MERRA).

I believe this process can be described using a conceptual model:

Imagine a cup of water with green beans soaking in it, covered by a lid. When the lid is opened, water evaporates, and as the water level decreases, does the evaporation (per unit of time) also decrease? The answer is yes, indicating that groundwater (represented by the cup of water) influences evaporation.

Now, imagine the cup is topped by a sponge (representing the unsaturated zone). If we measure evaporation from the top of the sponge (which should represent actual evapotranspiration at the land surface), the evaporation will still decrease as the water in the cup (groundwater) decreases. However, there should be a time lag because groundwater evaporation reaches the sponge first.

This concept is especially relevant for soils, where soil evaporation is derived from both past groundwater evaporation and past precipitation infiltration. Similarly, for vegetation transpiration, a rising water table would lead to increased water uptake by vegetation, thereby increasing transpiration. Again, a time lag would be expected in this process.

In other words, according to this conceptual model, actual evapotranspiration at the land surface tends to lag behind groundwater evaporation.

With this in mind, is it correct that groundwater recharge analysis should subtract evapotranspiration from precipitation and then calculate recharge per unit of time? In particular, in some common response analyses, recharge is considered as the net of precipitation minus evaporation, and then the groundwater time series is fitted with a gamma function or other response functions. However, doesn't this treatment implicitly assume that higher evaporation leads to lower groundwater levels in the future?

However, shouldn't evaporation be a “sink” rather than a “source” of groundwater? Shouldn't the only components of evapotranspiration that affect recharge be vegetation indicating interception losses and soil interception?

Please let me know your answer.

I want to know whether gravel formed in river by natural process is better than the gravel made in crusher from any perspective. Please, share your experience and knowledge.

I am working on enhancing the SWAT+ model for my PhD research and need to modify its source code. Could anyone suggest:

Any guidance would be greatly appreciated. Thank you!

I need documentation and research on how hyalite is formed in outwash glacial deoposits on granitic/andesitic cobbles and river beds. I am finding this material on outwash sands and gravels at approximately 30-36 inches below soil level throughout the Puget Sound (Salish Sea) basin. I have also found it from Spokane, WA to the Pacific coast, from Canada to Eugene, Oregon.

This deposit is above glacial till levels, and primarily outwash deposits and river beds. Most documentation I find talks about hyalite occurring in volcanic regions deep within the rocks in cracks and cavities. This material I speak of is ubiquitous across Washington and parts of Oregon. Landscape cobbles from Montana show the same material.

Calcite (calcium carbonate) deposits from river bed rocks in New Jersey for example look completely different, showing mineral versus glass-like composition, nor do the "joins" between two rocks look the same.

Originally by the looks of it, occurring on one side of the rocks only and showing signs of high viscosity I and my research associates thought it was impact meltglass, until we learned it was analyzed at the University of Washington under SEM analysis as Hyalite, hydrated silicon dioxide (SiO₂·nH₂O). Not only can we not call it impact melt glass because of the chemical composition, but also because SEM and magnetic analyses of spherules and pieces of "meltglass" show that the impact proxies were made in a highly charged magnetic field, indicating lightning may have created the "meltglaze" we call the hyalite on the rocks.

It is known that lightning can beat up rocks and create the same proxies for impacts as comet or asteroid explosions can. So either:

a) Am I getting lucky gathering rock and soil samples at lightning strike locations everyhwhere all the time, or

b) If the magnetic charge is ubiquitous regionally, do we need to include lightning as a byproduct of impact that results from regional spontaneous combustion/vaporization of forests? Wildfires in Australia in the last decade have generated their own weather and lightning from the ferocity of the blazes.

In each site I look at there is ample evidence of widepread wildfires, with a burn layer right on glacial till, or within 24 inches (60 cm) below soil level. Therefore the hyalite layer occurs below that from 30 to 39 inches bsl.

I would appreciate whatever people can find, thank you.

I have modeled the PMF of of a particular river but the available observed discharges are too small compared to the PMF value so, how do i calibrate the model with this limitation. thak you

Book Theme: The rivers of India, vital lifelines that support agriculture, industry, and drinking water needs, are facing unprecedented challenges due to climate change and human activities of the Anthropocene. The impact of rising temperatures, altered precipitation patterns, and increasing frequency of extreme weather events is profoundly affecting the geomorphology, hydrology, ecology, and socioeconomic fabric associated with these waterways. This book project (edited volume) explores how climate change is influencing Indian rivers (impact) and outlines potential strategies for mitigation and adaptation (resilience). It also covers the impact of various human activities on the fluvial morphology, hydrology, and riverine environment. Yet, as we step further into the 21st century, these vital waterways face unprecedented challenges. Reviving and restoring fluvial ecosystems is essential for reviving the health of India's rivers. This involves rehabilitating wetlands, reforesting riparian zones, and restoring natural river channels that have been altered by human activity. The need to reimagine and revitalize India's rivers has never been more urgent. To ensure their sustainability and health, a comprehensive blueprint is essential—one that balances ecological preservation with socioeconomic development. Research initiatives from a range of academic perspectives, including geography, biology, hydrology, geomorphology, environmental sustainability, environmental science, water economy, sociology, and political geography, are required for the book project.

In your opinion, which programming language would you suggest as the best choice for researchers specializing in hydrology and water resources?