question: Why doesn’t the water in lakes and rivers get absorbed into the ground?
comment: Some do lose water due to seepage. They lose more or less depending on what kind of rock and sediment lies beneath the lake. A rocky bottom holds water better than a sandy bottom. Lakes are also subject to evaporation from their surfaces – especially in a dry places – for example, the American West. So why don’t lakes just dry up? Some do. For a lake to keep its water over time, it has to be replenished. There are both natural and man-made lakes. The main way that water gets into reservoirs and man-made lakes is from the rivers and streams that were dammed to create them. Like man-made reservoirs and lakes, natural lakes may also be replenished by rivers and streams. Natural lakes have another advantage, when it come to holding their water. They tend to form in the lowest elevations in a given area. So these sorts of lakes may also get underground water that flows in from underneath the lake – the lake floor may be an area of water input, rather than a drain for the lake.
passages: The occurrence of a lake capture is mainly controlled by the water balance at the lake's basin and the changes in topography due to erosion, sedimentation, and tectonism. If evaporation at the surface of a lake, plus the water losses through underground infiltration and plant evapotranspiration are high enough to account for all precipitation water collected by the lake, then the lake becomes endorheic, closed, or internally drained. This situation prevails until the water balance changes again and the lake overburdens the limits of its basin or until the lake capture occurs. Opening the drainage of an endorheic lacustrine basin by fluvial erosion generally implies a lake capture.
   Even within exorheic basins, there can be "non-contributing", low-lying areas that trap runoff and prevent it from contributing to flows downstream during years of average or below-average runoff. In flat river basins, non-contributing areas can be a large fraction of the river basin, e.g. Lake Winnipeg's basin. A lake may be endorheic during dry years and can overflow its basin during wet years, e.g., the former Tulare Lake.
   Subsurface water may return to the surface in groundwater flow, such as from a spring, seep, or a water well, or subsurface return to streams, rivers, and oceans. Water returns to the land surface at a lower elevation than where infiltration occurred, under the force of gravity or gravity induced pressures. Groundwater tends to move slowly, and is replenished slowly, so it can remain in aquifers for thousands of years. Mainly, water flows through the ground which leads to the ocean where the cycle begins again.
  
  Section::::Subsurface flow.
   After water infiltrates the soil on an up-slope portion of a hill, the water may flow laterally through the soil, and exfiltrate (flow out of the soil) closer to a channel. This is called subsurface return flow or throughflow.
  
  As it flows, the amount of runoff may be reduced in a number of possible ways: a small portion of it may evapotranspire; water may become temporarily stored in microtopographic depressions; and a portion of it may infiltrate as it flows overland. Any remaining surface water eventually flows into a receiving water body such as a river, lake, estuary or ocean.
   In addition to causing water erosion and pollution, surface runoff in urban areas is a primary cause of urban flooding which can result in property damage, damp and mold in basements, and street flooding.
  
  Section::::Generation.
  
   Surface runoff can be generated either by rainfall, snowfall or by the melting of snow, or glaciers.
   BULLET::::- Runoff: The variety of ways by which water moves across the land. This includes both surface runoff and channel runoff. As it flows, the water may seep into the ground, evaporate into the air, become stored in lakes or reservoirs, or be extracted for agricultural or other human uses.
  
  BULLET::::- Infiltration: The flow of water from the ground surface into the ground. Once infiltrated, the water becomes soil moisture or groundwater. A recent global study using water stable isotopes, however, shows that not all soil moisture is equally available for groundwater recharge or for plant transpiration.
   One source of groundwater organic matter is soil organic matter and sedimentary organic matter. The major method of movement into soil is from groundwater, but organic matter from soil moves into groundwater as well. Most of the matter in lakes, rivers, and surface water areas comes from deteriorated material in the water and surrounding shores, and some from groundwater.
  
  This movement enables a cycle to form. Organisms decompose into organic matter, which is then transported and recycled. Not all biomass migrates, some is rather stationary, turning only over the course of millions of years.
  
  Section::::Soil organic matter.
   Section::::Sources of streamflow.
  
  Surface and subsurface sources: Stream discharge is derived from four sources: channel precipitation, overland flow, interflow, and groundwater.
  
  BULLET::::- Channel precipitation is the moisture falling directly on the water surface, and in most streams, it adds very little to discharge. Groundwater, on the other hand, is a major source of discharge, and in large streams, it accounts for the bulk of the average daily flow.
   Atmospheric circulation moves water vapor around the globe; cloud particles collide, grow, and fall out of the upper atmospheric layers as precipitation. Some precipitation falls as snow or hail, sleet, and can accumulate as ice caps and glaciers, which can store frozen water for thousands of years. Most water falls back into the oceans or onto land as rain, where the water flows over the ground as surface runoff. A portion of runoff enters rivers in valleys in the landscape, with streamflow moving water towards the oceans. Runoff and water emerging from the ground (groundwater) may be stored as freshwater in lakes. Not all runoff flows into rivers; much of it soaks into the ground as infiltration. Some water infiltrates deep into the ground and replenishes aquifers, which can store freshwater for long periods of time. Some infiltration stays close to the land surface and can seep back into surface-water bodies (and the ocean) as groundwater discharge. Some groundwater finds openings in the land surface and comes out as freshwater springs. In river valleys and floodplains, there is often continuous water exchange between surface water and ground water in the hyporheic zone. Over time, the water returns to the ocean, to continue the water cycle.
   As the groundwater is pumped out, the effective stress changes, precipitating consolidation, which is often non-reversible. Thus, the total volume of the silts and clays is reduced, resulting in the lowering of the surface. The damage at the surface is much greater if there is differential settlement, or large-scale features, such as sinkholes and fissures.
   then hydrostatic conditions will prevail and the fluids will not be flowing through the soil. formula_50 is the depth below the water table. However, if the water table is sloping or there is a perched water table as indicated in the accompanying sketch, then seepage will occur. For steady state seepage, the seepage velocities are not varying with time. If the water tables are changing levels with time, or if the soil is in the process of consolidation, then steady state conditions do not apply.
  
  Section::::Seepage: steady state flow of water.:Darcy's law.
   Section::::Consolidation analysis.
  
  Section::::Consolidation analysis.:Spring analogy.
  
  The process of consolidation is often explained with an idealized system composed of a spring, a container with a hole in its cover, and water. In this system, the spring represents the compressibility or the structure of the soil itself, and the water which fills the container represents the pore water in the soil.
  
  BULLET::::1. The container is completely filled with water, and the hole is closed. (Fully saturated soil)
   Changes in the level of a lake are controlled by the difference between the input and output compared to the total volume of the lake. Significant input sources are precipitation onto the lake, runoff carried by streams and channels from the lake's catchment area, groundwater channels and aquifers, and artificial sources from outside the catchment area. Output sources are evaporation from the lake, surface and groundwater flows, and any extraction of lake water by humans. As climate conditions and human water requirements vary, these will create fluctuations in the lake level.
   Open lakes typically have stable levels which do not fluctuate because input is always matched by outflow to rivers downstream. If more water enters an open lake than was previously leaving it, then more water will leave the lake. The drainage from an open lake, like that from ordinary rivers, is referred to as exorheic (from the Greek "exos", outside and "rhein", to flow).
  
  Section::::Closed lake.
   Denudation is the process of wearing away the top layers of Earth's landscape. Because the rate of denudation is normally too small to directly measure, it can be indirectly determined by measuring the sediment load of the streams that drain the area in question. This is possible because any material that passes through a certain point on a stream is guaranteed to have come from somewhere in the stream's drainage basin upstream of that point. As topographic relief increases, the dissolved load's contribution to the total stream load decreases due to the fact that on steeper surfaces, rain is less likely to infiltrate the rocks, leading to less chemical weathering, which decreases the dissolved load.
   Section::::Human influence.
  
  Urbanization increases surface runoff by creating more impervious surfaces such as pavement and buildings that do not allow percolation of the water down through the soil to the aquifer. It is instead forced directly into streams or storm water runoff drains, where erosion and siltation can be major problems, even when flooding is not. Increased runoff reduces groundwater recharge, thus lowering the water table and making droughts worse, especially for agricultural farmers and others who depend on the water wells.
   In areas where there is no snow, runoff will come from rainfall. However, not all rainfall will produce runoff because storage from soils can absorb light showers. On the extremely ancient soils of Australia and Southern Africa, proteoid roots with their extremely dense networks of root hairs can absorb so much rainwater as to prevent runoff even when substantial amounts of rain fall. In these regions, even on less infertile cracking clay soils, high amounts of rainfall and potential evaporation are needed to generate any surface runoff, leading to specialised adaptations to extremely variable (usually ephemeral) streams.
   Water level management is important in these lowland areas, and the local watercourses are usually maintained by internal drainage boards and their successors, with improved drainage being assisted by the use of pumping stations to lift water into embanked carrier rivers, which subsequently discharge into the Trent.
   Section::::Processes.:Depression-focused recharge.
  
  If water falls uniformly over a field such that field capacity of the soil is not exceeded, then negligible water percolates to groundwater. If instead water puddles in low-lying areas, the same water volume concentrated over a smaller area may exceed field capacity resulting in water that percolates down to recharge groundwater. The larger the relative contributing runoff area is, the more focused infiltration is. The recurring process of water that falls relatively uniformly over an area, flowing to groundwater selectively under surface depressions is depression focused recharge. Water tables rise under such depressions.
  
  Section::::Processes.:Depression-focused recharge.:Depression pressure.
   While the water cycle is itself a biogeochemical cycle, flow of water over and beneath the Earth is a key component of the cycling of other biogeochemicals. Runoff is responsible for almost all of the transport of eroded sediment and phosphorus from land to waterbodies. The salinity of the oceans is derived from erosion and transport of dissolved salts from the land. Cultural eutrophication of lakes is primarily due to phosphorus, applied in excess to agricultural fields in fertilizers, and then transported overland and down rivers. Both runoff and groundwater flow play significant roles in transporting nitrogen from the land to waterbodies. The dead zone at the outlet of the Mississippi River is a consequence of nitrates from fertilizer being carried off agricultural fields and funnelled down the river system to the Gulf of Mexico. Runoff also plays a part in the carbon cycle, again through the transport of eroded rock and soil.
   BULLET::::- Interflow is water that infiltrates the soil and then moves laterally to the stream channel in the zone above the water table. Much of this water is transmitted within the soil itself, some of it moving within the horizons. Next to baseflow, it is the most important source of discharge for streams in forested lands. Overland flow in heavily forested areas makes negligible contributions to streamflow.
   Groundwater can be a long-term 'reservoir' of the natural water cycle (with residence times from days to millennia), as opposed to short-term water reservoirs like the atmosphere and fresh surface water (which have residence times from minutes to years). The figure shows how deep groundwater (which is quite distant from the surface recharge) can take a very long time to complete its natural cycle.
   An open lake is a lake where water constantly flows out under almost all climatic circumstances. Because water does not remain in an open lake for any length of time, open lakes are usually fresh water: dissolved solids do not accumulate. Open lakes form in areas where precipitation is greater than evaporation. Because most of the world's water is found in areas of highly effective rainfall, most lakes are open lakes whose water eventually reaches the sea. For instance, the Great Lakes' water flows into the St. Lawrence River and eventually the Atlantic Ocean.
   Other soils may have an impervious layer of mineralized soil, called a hardpan or relatively impervious rock layers may underlie shallow soils. Drainage is especially important in tree fruit production. Soils that are otherwise excellent may be waterlogged for a week of the year, which is sufficient to kill fruit trees and cost the productivity of the land until replacements can be established. In each of these cases appropriate drainage carries off temporary flushes of water to prevent damage to annual or perennial crops.
   The hyporheic zone and its interactions influence the volume of stream water is moved downstream. Gaining reaches indicate that groundwater is discharged into the stream as water moves downstream, so that the volume of water in the main channel increases from upstream to downstream. Conversely, when water infiltrates into the groundwater zone resulting in a net loss of surface water, the stream reach is considered to be "losing" water. 
  
  Section::::Studying the Hyporheic Zone.
  
presuppositions: Water in lakes and rivers is not absorbed into the ground. Water in lakes and rivers is never absorbed into the ground.
corrections: Water in lakes and rivers can be absorbed into the ground. Some lakes and rivers do lose water due to seepage.
raw_presuppositions: Water in lakes and rivers is not absorbed into the ground. Water in lakes and rivers is never absorbed into the ground.
raw_corrections: Water in lakes and rivers can be absorbed into the ground. Some lakes and rivers do lose water due to seepage.