Analyzing Dam Seepage Using MODFLOW, How to Start?

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.

The spatial scene is defined as a collection of spatial objects and their particular spatial arrangement (Nedas, 2008). In the city scene, road and building are two fundamental elements for urban structure analysis. There are various pattern types due to the spatial distribution of building and road(e.g. linear buildings along the straight road, etc.).

I would like to know the typology of spatial scene patterns, or if there are any relevant literatures discussing them.

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.

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