Water retention and runoff formation in the Krkonoše Mts

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1 ŠÍR M. & TESAŘ M. 2013: Water retention and runoff formation in the Krkonoše Mts. Opera Corcontica 50/S: Water retention and runoff formation in the Krkonoše Mts Retence vody a formování odtoku v Krkonoších MILOSLAV ŠÍR & MIROSLAV TESAŘ Academy of Sciences of the Czech Republic, Institute of Hydrodynamics, Pod Paťankou 30/5, Praha 6, CZ, milo_sir@yahoo.com, tesarihas@iol.cz Abstract Water retention and runoff formation have been studied in two basins located in the Giant Mts (Krkonoše in Czech, Karkonosze in Polish). The Labe basin (LB: area km 2, altitude 692 to 1,503 m a.s.l.), and the Modrý Potok basin (MP: area 2.62 km 2, altitude 1,010 to 1,554 m a.s.l.) are located in the same natural conditions. The bedrock is formed by rocks of the crystalline complex. The prevailing soil types are Humic Podzols, Lithic Leptosols, and Dystric Histosol. The vegetative cover is formed by grass and spruce forest in the lower part, and artic-alpine tundra with dwarf pine in the upper part above the timberline. In September 2001, unusual rainfall of 348 mm/mo (LB) and 364 mm (MP) fell. Consequently, a runoff of 281 mm/mo (LB) and 262 mm/mo (MP) was generated. The maximum retention of water in the basin was 80 mm (LB) and 140 mm (MP). At the moment of peak runoff, water retention in the basins captured 40 % (LB) and 65 % (MP) of previous cumulative rain. In the Labe basin, anomalous fill-spill effect was observed: water supplied by rain caused a decrease of 40 mm in the soil water content. This resulted in a reduction of the water retention by 5 mm in the Labe basin. The conclusion, gained in both basins, is that the retention of water in the basin and particularly in the soil profile significantly reduced the peak runoff from the watershed. Keywords: mountain hydrology, runoff formation, catchment water retention, soil water movement Abstrakt Ve dvou povodích v Krkonoších se studovala retence vody a formování odtoku. Povodí Labe (LB: plocha 53,06 km 2, nadmořská výška 692 až m n. m.) a povodí Modrý potok (MP: plocha 2,62 km 2, nadmořská výška až m n. m.) se nacházejí ve shodných přírodních podmínkách. Geologické podloží je tvořeno krystalinikem. Převažujícími půdními typy jsou podzoly, leptosoly a organosoly. Vegetační pokryv je tvořen v nižších polohách travním porostem a smrkovým lesem. Nad hranicí lesa se nachází arkticko-alpinská tundra s klečovým porostem. V září 2001 na obě povodí spadla série dešťů s neobvykle vysokým úhrnem 384 mm/měsíc (LB) a 364 m/měsíc (MP). Následkem byl vysoký měsíční odtok, který dosáhl 281 mm/měsíc (LB) a 262 mm/měsíc (MP). Maximální retence dešťové vody v povodí v srpnu 2001 dosáhla 80 mm (LB) a 140 mm (MP). Při největším průtoku v uzávěrovém profilu povodí dosáhla retence vody v povodí 40 % (LB) a 65 % (MP) kumulativní srážky od počátku měsíce do okamžiku největšího průtoku. Na měřícím stanovišti v povodí Labe (LB) bylo pozorováno anomální proudění vody v půdě, při kterém déšť vsakující do půdy způsobil pokles zásoby vody v půdě o 40 mm. Tento jev se projevil snížením retence vody v celém povodí o 5 mm. V obou povodích byl získán shodný závěr, že retence dešťové vody v povodí, a zvláště v půdním profilu, podstatně snižuje maximální odtok vody z povodí při dlouhodobých deštích o vysokém úhrnu. Klíčová slova: horská hydrologie, formování odtoku, retence vody v povodí, pohyb půdní vody Introduction Several crucial factors contribute to runoff formation; rainfall intensity and its total, water retention in a catchment, and hydrophysical properties of soil and subsoil including water retention in the soil cover. A key issue in the research of runoff is the evaluation of the share of each of these processes affecting runoff formation (KOSTKA & HOLKO 1997, TESAŘ et al. 2004a, 2004b, 2008, 2010, TROMP-VAN MEERVELD & MCDONNELL 2006a, 2006b). It was found that water retention in the soil and the entire basin significantly influences runoff formation (KOSTKA & HOLKO 1997). The crucial role

2 98 OPERA CORCONTICA 50/S 2013 of soil water in the runoff formation is well known because soil cover creates large water reservoirs (KUTÍLEK & NIELSEN 1994). In the Czech Republic, the retention capacity of the soil cover is one order higher than the volume of all artificial and natural water reservoirs. Typical water retention capacity of the soil cover ranges from 60 to 90 mm in the mountainous and submontane basins (DOLEŽAL et al. 2004). This study is devoted to the analysis of the runoff formation in two mountainous basins located in the Giant Mts, taking into account soil water movement and water retention in the catchments. Material and methods Water retention and runoff formation have been studied in two basins in the Giant Mts (Fig. 1). The Labe basin and the Modrý Potok basin are located in the same natural conditions. They differ mainly in the catchment area: the Labe basin is 20 times larger than the Modrý Potok basin. Nevertheless, in terms of experimental hydrology, both cases can be regarded as small basins (HERMANN & SCHUMANN 2010). The Labe basin is situated in the western part of the Giant Mts. The area of this basin is km 2. The highest point is the Vysoké Kolo Mt. (1,503 m a.s.l.) and the minimum elevation of the closing profile in the vicinity of Špindlerův Mlýn is 692 m a.s.l. The average annual rainfall total was 1,519 mm; average annual Fig. 1. The location of the Giant Mts, the Labe basin, the Labská Louka stand, and the Modrý Potok basin in the Czech Republic. Obr. 1. Poloha Krkonoš, povodí Labe, stanoviště Labská louka a povodí Modrý potok v České republice. depth of runoff was 1,271 mm; and the runoff coefficient was Average annual discharge in the closing profile was 2.14 m 3 /s; a 100-year flood is 175 m 3 /s. The Labská Louka stand is located in the Labe basin, close to the Labe river headspring, at an elevation of 1,370 m a.s.l. The climatic conditions correspond to the characteristics of the cold climatic zone (the average air temperature in January is about 6 C, in July from 10 C to 12 C). The mean annual precipitation total ranges from 1,300 to 1,500 mm. The Labská Louka stand is situated on the flush surface (peneplain) of the bedrock. It consists of biotitic granite. The depth of the weathered zone ranges from units to tens of metres. The prevailing soil type is Dystric Histosol (WRB 1998). The physical geographic situation of the Labe basin is depicted in Fig. 2. On the Labská Louka stand, a monitoring station is located in the area covered by grass (marked as LLUM in Fig. 2). The Modrý Potok basin is located in the eastern part of the Giant Mts. The area of this basin is 2.62 km 2. The highest point is the Studniční hora Mt. (1,554 m a.s.l.) and the minimum elevation of the closing profile is 1,010 m a.s.l. There are deposits of fluvial or fluviodeluvial sediments along the Modrý Potok brook. The soil types are Humic Podzols and Lithic Leptosols (WRB 1998) with a very thin humic layer. Deeper soil of about 60 cm can be found in the bottom part of the valley. The original spruce forest is represented in the lower part of this basin, and artic-alpine tundra with dwarf pine covers the upper part above the timberline. Climatic conditions correspond to the characteristics of the cold humid climatic zone. The mean annual precipitation total ranges from 1,200 to 1,300 mm. The mean air temperature in July is 12.1 C. The maximum retention of water in the basin is about 70 mm (TESAŘ et al. 2004a). The physical geographic situation of the Modrý Potok basin is shown in Fig. 3. A monitoring station is placed in a valley meadow located below the forest margin (marked as VM in Fig. 3). Monitoring stations in the Modrý Potok basin and the Labe basin are located at an aerial distance of 13 km from each other. The following parameters have been measured at each monitoring station: rain intensity and total, global radiation, air temperature at two levels (5 and 200 cm above the soil surface), soil temperature at three depths (15, 30, 60 cm), the tensiometric pressure in the soil cover at four depths (15, 30, 45, 60 cm), and the averaged soil moisture content in the soil layer of 0 60 cm. Tensiometric pres-

3 ŠÍR & TESAŘ: WATER RETENTION AND RUNOFF 99 Fig. 2. Physical geographic situation of the Labe basin with closure profile in the vicinity of Špindlerův Mlýn (CPSM) and monitoring stations located in the Labská Louka meadow stand (LLUM the Labská Louka upper meadow). Obr. 2. Fyzicko-geografická situace povodí Labe s uzávěrovým profilem v blízkosti Špindlerova Mlýna (CPSM) a poloha monitorovacích stanic umístěných na Labské louce (LLUM Labská louka, horní louka). Fig. 3. Physical geographic situation of the Modrý Potok basin and position of monitoring stations. MSV meteorological station Výrovka chalet; CPMP closure profile of the Modrý Potok basin; VM valley meadow located below the forest margin; SF mature spruce forest; UM upper meadow located above the forest margin; DW dwarf pine forest located above the forest margin. Obr. 3. Fyzicko-geografická situace povodí Modrý potok a poloha monitorovacích stanic. MSV meteorologická stanice u chaty Výrovka, CPMP uzávěrový profil povodí Modrý potok, VM údolní louka pod hranicí lesa, SF dospělý smrkový les, UM horní louka nad hranicí lesa, DW klečový porost nad hranicí lesa.

4 100 OPERA CORCONTICA 50/S 2013 sure was measured by water tensiometers. The soil moisture was determined using high frequency permittivity measurement (LICHNER et al. 2004). All values were recorded at ten-minute steps. The discharge at the closing profile of the Modrý Potok basin was measured using a pressure sensor and recorded at ten-minute steps. Runoff depth from entire basin area was determined as a discharge in the closing profile of a basin divided by the catchment area. Hourly sums of precipitation total and runoff depth were used for evaluation of actual water retention in the Modrý Potok basin. To calculate the actual water retention in the Labe basin, hourly sums of precipitation total and runoff depth provided by the CHMI were used. Evapotranspiration from both basins was determined with the help of the method described in the article of PRAŽÁK et al. (1994) using hourly values of air temperature and hourly totals of global solar radiation measured in monitoring station placed close to the Výrovka chalet on the watershed divide between both basins (marked as MSV in Fig. 3). The time course of cumulative rainfall depth was obtained by adding hourly precipitation from the beginning to the end of September Similarly, the time course of cumulative runoff depth was obtained. Cumulative rainfall depth and cumulative runoff depth were expressed in millimetres of water column. Actual water retention in an entire basin area was derived as the difference between the cumulative rainfall depth and cumulative runoff depth assuming negligible transpiration (CZELIS & SPITZ 2003). Thus, the determined value is actually an increase or decrease of water content in the basin to the unknown initial value at the beginning of September Actual water retention was calculated in millimetres of water column. Results Seven distinctive rain events were observed in the Modrý Potok meteorological station and the Labská Louka stand in September Four major discharge events were caused by four rain events (Fig. 4). Rain courses were very similar so that distinctive rain events corresponded in both basins (Fig. 4). The beginnings and ends of rain events were almost identical, and monthly rainfall depths were very similar (Tab. 1). A difference of about 5% is smaller than the standard uncertainty of about 10%, which is caused by rain variability (LAPIN & FAŠKO 1997). Monthly rainfall depth in the range of mm formed 23 24% of the average annual rainfall total. This means that the discussed monthly rainfall was extreme. Fig. 4. Cumulative rain in the Modrý Potok basin and the Labská Louka meadow stand in September P1 to P7 denote distinctive rain events. Obr. 4. Kumulativní srážky v povodí Modrý potok a na stanovišti Labská louka v září P1 až P7 označují výrazné deště.

5 ŠÍR & TESAŘ: WATER RETENTION AND RUNOFF 101 Tab. 1. Runoff coefficients in the Labe basin and the Modrý Potok basin in September Tab. 1. Odtokové koeficienty v povodí Labe a v povodí Modrý potok v září Monthly rain sum (mm) Monthly runoff sum (mm) Runoff coefficient ( ) Labe basin Modrý Potok basin In the Fig. 5, runoff and cumulative runoff in both basins are depicted. The runoff values in both basins were very similar (Fig. 5). The beginnings and ends of flood waves in both basins were almost identical, and the monthly runoffs of mm were very similar (Tab. 1). In the Labe basin, the maximum monthly discharge of m 3 /s was reached at 10 am on 10 th September. In the Modrý Potok basin, peak discharge of m 3 /s was achieved about two hours later. The evapotranspiration was negligible (approx. 10 mm/mo) throughout September 2001, due to steady rain and low air temperature. Therefore, the actual water retention in a basin was derived as the difference between the cumulative rain depth and cumulative runoff depth from the entire basin supposing that the very small evapotranspiration can be ignored (CZELIS & SPITZ 2003). Fig. 6 presents water retention in the Modrý Potok basin and the Labe basin and their difference in September The arrow 140 mm denotes maximum water retention in the Modrý Potok basin. The arrow 80 mm denotes maximum water retention in the Labe basin. The arrow 60 mm denotes the maximum difference between water retention in both basins. As shown in Fig. 6, water retention played a significant role in runoff formation in both basins. The maximum water retention in the Modrý Potok basin during the rain P3 (at 8 am on 10 th September) can be estimated at 140 mm. At this moment, the cumulative rain for September was 216 mm/mo. This means that 65% of the cumulative rain was stored in the basin and 35% formed cumulative runoff. The maximum water retention in the Labe basin during the rain P3 (10 pm on 10 th September) was 80 mm (Fig. 6). At this moment, the cumulative rain for September was 200 mm. This means that 40% of the cumulative rain was stored in the basin, and 60% of the cumulative rain formed cumulative runoff. The amount of water retained in the basin at the time of maximum retention can be estimated as follows: km 2 x 80 mm = 4.3 million m 3. This huge volume of water exceeded the total volume of million m 3 of the Labská reservoir located downstream of the closing profile of the Labe basin. The catchment area of the Labská reservoir is km 2, which is Fig. 5. Runoff and cumulative runoff in the Modrý Potok basin and Labe basin in September D1 to D4 denote discharges caused by rain events P1 to P4 (see Fig 4). Obr. 5. Odtok a kumulativní odtok z povodí Modrý potok a povodí Labe v září D1 až D4 označují výrazné odtokové vlny zapříčiněné dešti P1 až P4 (viz obr. 4).

6 102 OPERA CORCONTICA 50/S 2013 Fig. 6. Water retention in the Modrý Potok basin and Labe basin, and their differences in September Arrow 140 mm denotes maximum water retention in the Modrý Potok basin. Arrow 80 mm denotes maximum water retention in the Labe basin. Arrow 60 mm denotes maximum difference between water retention in both basins. Obr. 6. Retence vody v povodí Modrý potok a povodí Labe a rozdíl retence vody v obou povodích v září Šipka 140 mm značí maximální retenci vody v povodí Modrý potok. Šipka 80 mm značí maximální retenci vody v povodí Labe. Šipka 60 mm označuje maximální rozdíl retence vody v obou povodích. Fig. 7. Water retention, cumulative rain, and cumulative runoff in the Labe basin in the period of 5 11 th September P1 and P2 denote distinctive rain events; arrows RA, RB, RC denote water retention at times A, B, C. Obr. 7. Retence vody, kumulativní srážka a kumulativní odtok v povodí Labe v období září P1 a P2 značí výrazné deště, šipka RA, RB, RC značí retenci vody v okamžicích A, B, C.

7 ŠÍR & TESAŘ: WATER RETENTION AND RUNOFF 103 close to the catchment area of the studied Labe basin km 2. This example shows why the flood risk in submontane areas, resulting from the small retention capacity of mountain basins, cannot be entirely eliminated by the construction of dams and reservoirs in river valleys, although they can significantly reduce flood damage. Fig. 7 illustrates water retention, cumulative precipitation and cumulative runoff in the Labe basin in the period of 5 11 th September P1 and P2 denote distinctive rain events; arrows RA, RB, RC denote water retention at times A (at 10 am on 8 th September), B (at noon on 9 th September), and C (at midnight on 11 th September). In time B, the water retention decreased compared to time A. Fig. 8 shows the same episode in the Modrý Potok basin. Fig. 9 represents the soil water content and cumulative precipitation in the Labská Louka stand in the period of 5 11 th September, The arrow 40 mm denotes the drop in the soil water content between A and B (at noon on 9 th September). At time A, the soil water content in the soil layer of 0 60 cm reached a maximum value of 238 mm. In the time interval A B, the infiltration of 10-mm rainwater induced Fig. 8. Water retention, cumulative rain, and cumulative runoff in the Modrý Potok basin in the period of 5 11 th of September P1 and P2 denote distinctive rain events; arrows RA, RB, RC denote water retention at times A, B, C. Obr. 8. Retence vody, kumulativní srážka a kumulativní odtok v povodí Modrý potok v období září P1 a P2 značí výrazné deště, šipka RA, RB, RC značí retenci vody v okamžicích A, B, C. Fig. 9. Soil water content and cumulative rain in the Labská Louka meadow stand in the period of 5 11 th September Arrow 40 mm denotes the drop in the soil water content at time B caused by the fill-spill effect. Obr. 9. Zásoba vody v půdě a kumulativní srážky na stanovišti Labská louka v období září Šipka 40 mm značí pokles zásoby vody v půdě v okamžiku B způsobený anomálním prouděním vody v půdě.

8 104 OPERA CORCONTICA 50/S 2013 the outflow of 37-mm water stabilised in the soil before the rain. Therefore, the total outflow of rain and soil water from the soil profile into the bedrock was 47 mm. This phenomenon, known as the fillspill effect, caused substantial drying of the soil cover (Fig. 9) and reduced the water retention by 5 mm in the Labe basin (arrow RB in Fig 7). Tab. 1 shows monthly rainfall totals, monthly runoff depths, and runoff coefficients in both basins. Runoff coefficient is the fraction of runoff depth and rainfall total. Monthly runoff coefficients in the range of seem to be quite high; however, they closely match the long-term runoff coefficient of 0.84 in the Labe basin. The unusually high longterm runoff coefficient is mainly caused by the melting of the huge volume of snow accumulated in the highest areas of the basin in the spring. Discussion The physics of the fill-spill effect is the subject of contemporary research activities (GLASS & YARRINGTON 2003, FÜRST et al. 2009). TESAŘ et al. (2004b) gave the following description of the fill-spill effect. In the basin Liz (Czech Republic, Bohemian Forest), two coupled anomalous phenomena in soil water flow were observed: (1) in some situations, the water supplied by rain caused a pronounced decrease in the soil water content. (2) In these periods, the soil water movement could be explained only by assuming an irregularly oscillating outflow of soil water into lower horizons. An explanation of the oscillatory discharge of soil water is given in the article by PRAŽÁK et al. (1992). When the soil moisture content exceeds a certain threshold value, gravity-driven flow of the soil water arises. In such a situation, a large volume of water starts to flow through the soil into the bedrock (spill phase). When the soil moisture content drops below the threshold value, gravity-driven flow vanishes and it is replaced by diffusion flow, during which water moves slowly from the soil into the bedrock (fill phase). Therefore, the fill-spill effect can be formulated as follows: There is a threshold value of the soil moisture content. If the soil moisture content is smaller than the threshold value, water is filling soil pores (fill phase) without leaking into the underlying bedrock. If the soil moisture content is greater, water is released from the soil (spill phase). In the Labe basin, the threshold value of the volumetric soil water content is approx. 40%. This corresponds to the maximum value of the soil water content of 240 mm in the soil layer of 0 60 cm at time A (at 10 am on 8 th September) in Fig. 9. The fill-spill effect is characterised by non-monotonicity of the soil saturation pattern: the soil saturation first increases (during the fill phase) and then, despite the continuous influx of rain water, it starts decreasing (during the spill phase). This non-monotonicity is called saturation overshoot. An example of the saturation overshoot is shown in Fig. 9. The spill phase begins in time A when the soil water content is maximal and ends at time B when the soil water content is minimal. Saturation overshoot in gravity-driven fingers was experimentally observed by GLASS et al. (1989), SEL- KER et al. (1992) and LIU et al. (1994) and many others. The most comprehensive experimental work was done by BAUTERS et al. (2000) and DICARLO (2004, 2007). FÜRST et al explained why saturation overshoot can never be obtained as a solution of the Richards equation (KUTÍLEK & NIELSEN 1994). Consequently, this effect remains outside the scope of standard porous media flow models often used for description of the soil water movement. During the fill-spill effect, a large volume of water flows through the soil into the bedrock (TESAŘ et al. 2004b). Therefore, at the basin scale, this phenomenon creates some part of the runoff. Let us make a highly speculative estimate of the volume of water that was drained due to the fill-spill effect from the soil cover into bedrock in the period of 5 11 th September, 2001 in the Labe basin. The quantity of water, which was released from the Labe basin during the fill-spill effect, can be estimated as follows: km 2 x 5 mm = 0.3 million m 3. If we submit that the retention of water in the Labe basin in the absence of fill-spill effect would have increased by 10 mm, as in the Modrý Potok basin (arrow RB in Fig. 8), then this would be the discussed volume of km 2 x 5 mm km 2 x 10 mm = 0.8 million m 3. The size of the area probably affected by the fillspill effect can be ranged by these limits: minimum = km 2 x 5/40 mm = 6.6 km 2, maximum = km 2 x 15/40 mm = 19.9 km 2. This means that 13 to 38 % of the entire basin area could be affected by the fill-spill effect. The fill-spill effect often occurs at high soil saturation (TESAŘ et al. 2004a, 2008, 2010). This means that

9 ŠÍR & TESAŘ: WATER RETENTION AND RUNOFF 105 hydrologic conditions, in which the fill-spill effect may occur, can be a source of flood risk, especially in the case of flash floods. The fill-spill effect was observed in the Bohemian Forest, the Giant Mts and other mountains (PRAŽÁK et al. 1992, TROMP-VAN MEERVELD & MCDONNELL 2006a, 2006b). Understanding of soil water movement and runoff formation enables an increase in the lead time of runoff prediction, which is important for the design of early warning systems for flash floods detection (NOAA 2010). As an output of the above described findings concerning the spill-fill effect affecting outflow of water from the soil cover the early warning system (EWS) for flash floods was designed and created in the head water region of the Giant Mts (TESAŘ & ŠÍR, 2013). The commonly used EWS has been supplemented by the monitoring of the state (using water tensiometers) and amount (with the help of soil moisture meters) of water in the soil profile. Conclusions In September 2001, unusual rainfall of 348 mm/mo in the Labe basin (LB) and 364 mm/mo in the Modrý Potok basin (MD) fell. Consequently, a runoff of 281 mm/mo (LB) and 262 mm/mo (MD) was generated. The maximum water retention in the basins was 80 mm (LB) and 140 mm (MD). At the moment of peak runoff, water retention in the catchment captured 40 % (LB) and 65 % (MD) of cumulative rain. In the Labe basin, anomalous fill-spill effect was observed: water supplied by rain caused a decrease of 40 mm in the soil water content. This resulted in reducing water retention in the catchment by 5 mm. The conclusion, gained in both basins, is that the retention of water in the basin and particularly in the soil profile significantly reduced the peak runoff. These results suggest that, in both basins, similar rain triggered similar runoffs events, regardless of their significantly different basin area. Therefore, it can be reasonably assumed that due to the large similarity of natural conditions, identical transport processes affected on runoff formation. Consequently, it is possible to consider that the results obtained in two studied small basins are representative for the whole Giant Mts. This finding confirms the basic idea of hydrological research conducted in two studied small basins: mechanisms of runoff formation in a small basin should be the same as in a large basin assuming the same natural conditions (HERMANN & SCHUMANN 2010). Souhrn Příspěvek analyzuje retenci vody a formování odtoku na příkladu povodí Labe a povodí Modrého potoka v Krkonoších. V září 2001 tato místa ovlivnila výrazná dešťová episoda, kdy úhrn srážek dosáhl 384 mm/ měsíc resp. 364 mm/měsíc. To se následně projevilo i ve zvýšené měsíčným odtoku. Anomální proudění vody v půdě (tzv. fill-spill efekt), které bylo zaznamenáno na sledovaném ploše v Povodí Labe, však může ovlivnit (snížit) retenční schopnost dešťové vody v povodí a zvýšit rychlost odtoku. To hraje významnou roli pro predikci bleskových povodní. Podrobný monitoring těchto procesů je základem pro vybudování systému včasného varování. Acknowledgements The work has been supported by the Technology Agency of the Czech Republic (Project TA ). References BAUTERS T. W. J. DICARLO D. A. STEENHUIS T. & PARLANGE J.-Y. 2000: Soil water content dependent wetting front characteristics in sands. Journal of Hydrolology : CZELIS R. & SPITZ P. 2003: Retence vody v povodí při povodních. Acta Hydrologica Slovaca 4, 2: DICARLO D. A. 2004: Experimental measurements of saturation overshoot on infiltration. Water Resources Research 40: W04215, DOI: /2003WR DICARLO D. A. 2007: Capillary pressure overshoot as a function of imbibition flux and initial water content. Water Resources Research 43: W08402, DOI: /2006WR

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